Poly(acrylic acid) from bio-based acrylic acid and its derivatives

ABSTRACT

Bio-based glacial acrylic acid, produced from hydroxypropionic acid, hydroxypropionic acid derivatives, or mixtures thereof and having impurities of hydroxypropionic acid, hydroxypropionic acid derivatives, or mixtures thereof, is polymerized to poly(acrylic acid) or superabsorbent polymer using the same processes as petroleum-derived glacial acrylic acid.

FIELD OF THE INVENTION

The present invention generally relates to the production ofpoly(acrylic acid) (PAA) from bio-based acrylic acid, acrylic acidderivatives, or mixtures thereof produced from hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof. Morespecifically, the invention relates to the polymerization of bio-basedglacial acrylic acid, acrylic acid derivatives, or mixtures thereof toform PAA or superabsorbent polymer (SAP).

BACKGROUND OF THE INVENTION

Acrylic acid or acrylate has a variety of industrial uses, typicallyconsumed in the form of polymers. In turn, these polymers are commonlyused in the manufacture of, among other things, adhesives, binders,coatings, paints, polishes, detergents, flocculants, dispersants,thixotropic agents, sequestrants, and superabsorbent polymers, which areused in disposable absorbent articles including diapers and hygienicproducts, for example. Acrylic acid is commonly made from petroleumsources. For example, acrylic acid has long been prepared by catalyticoxidation of propylene. These and other methods of making acrylic acidfrom petroleum sources are described in the Kirk-Othmer Encyclopedia ofChemical Technology, Vol. 1, pgs. 342-369 (5^(th) Ed., John Wiley &Sons, Inc., 2004). Petroleum-based acrylic acid contributes togreenhouse emissions due to its high petroleum derived carbon content.Furthermore, petroleum is a non-renewable material, as it takes hundredsof thousands of years to form naturally and only a short time toconsume. As petrochemical resources become increasingly scarce, moreexpensive, and subject to regulations for CO₂ emissions, there exists agrowing need for bio-based acrylic acid or acrylate that can serve as analternative to petroleum-based acrylic acid or acrylate. Many attemptshave been made over the last 40 to 50 years to make bio-based acrylicacid or acrylate from non-petroleum sources, such as lactic acid (alsoknown as 2-hydroxypropionic acid), 3-hydroxypropionic acid, glycerin,carbon monoxide and ethylene oxide, carbon dioxide and ethylene, andcrotonic acid.

Petroleum-based superabsorbent polymer is made by polymerization ofpetroleum-based acrylic acid using methods described in Buchholz andGraham (eds), MODERN SUPERABSORENT POLYMER TECHNOLOGY, J. Wiley & Sons,1998, pages 69 to 117, or recent patent applications, for example U.S.Patent Applications 2009/0275470 and 2011/0313113. The petroleum-basedacrylic acid used in these methods is glacial acrylic acid with purityexceeding 98% and typically being 99.5% or higher. The typical majorimpurities in the petroleum-based glacial acrylic acid are propionicacid, acetic acid, maleic anhydride, maleic acid, acrolein, andfurfural. On the other hand, the major impurities in the bio-basedglacial acrylic acid, acrylic acid derivatives, or mixtures thereofproduced from hydroxypropionic acid, hydroxypropionic acid derivatives,or mixtures thereof, are propionic acid, acetic acid, andhydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof.

Accordingly, there is a need for commercially viable processes ofpolymerizing bio-based glacial acrylic acid, acrylic acid derivatives,or mixtures thereof produced from the dehydration of hydroxypropionicacid, hydroxypropionic acid derivates, or mixtures thereof, to PAA fordetergents, flocculants, and other applications; and SAP for use indiapers and other applications.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a superabsorbent polymercomposition is provided produced from an acrylic composition, whereinthe acrylic composition comprises an acrylic acid composition, whereinthe acrylic acid composition consists of acrylic acid, acrylic acidderivatives, or mixtures thereof, wherein the acrylic acid compositioncomprises at least about 98 wt % acrylic acid, acrylic acid derivatives,or mixtures thereof, and wherein a portion of the remaining impuritiesin the acrylic acid composition is hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof.

In another embodiment of the present invention, a poly(acrylic acid)composition is provided produced from an acrylic composition, whereinthe acrylic composition comprises an acrylic acid composition, whereinthe acrylic acid composition consists of acrylic acid, acrylic acidderivatives, or mixtures thereof, wherein the acrylic acid compositioncomprises at least about 98 wt % acrylic acid, acrylic acid derivatives,or mixtures thereof, and wherein a portion of the remaining impuritiesin the acrylic acid composition is hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof.

DETAILED DESCRIPTION OF THE INVENTION I Definitions

As used herein, the term “poly(acrylic acid)” refers to homopolymers ofacrylic acid, or copolymers of acrylic acid and other monomers.

As used herein, the term “superabsorbent polymer” refers to a polymerwhich is capable of absorbing within the polymer at least 10 times itsweight in deionized water, allowing for adjustment of the pH of thesystem.

As used herein, the term “ion-exchange capacity” refers to thetheoretical or calculated ion-exchange capacity of the polymer orpolymers in milliequivalents per gram (meq/g) assuming that eachun-neutralized acid or base group becomes neutralized in theion-exchange process.

As used herein, the term “acrylic composition” refers to a compositionthat includes an acrylic acid composition and other materials, such as,water, other solvents, or mixtures thereof.

As used herein, the term “acrylic acid composition” refers to acomposition that consists of acrylic acid, acrylic acid derivatives, ormixtures thereof.

As used herein, the term “distilled acrylic acid” refers to acomposition of acrylic acid with content of acrylic acid lower thanabout 94 wt %.

As used herein, the term “crude acrylic acid” refers to a composition ofacrylic acid with content of acrylic acid between about 94 wt % andabout 98 wt %.

As used herein, the term “glacial acrylic acid” refers to a compositionof acrylic acid with content of acrylic acid at least about 98 wt %.

As used herein, the term “bio-based” material refers to a renewablematerial.

As used herein, the term “renewable material” refers to a material thatis produced from a renewable resource.

As used herein, the term “renewable resource” refers to a resource thatis produced via a natural process at a rate comparable to its rate ofconsumption (e.g., within a 100 year time frame). The resource can bereplenished naturally, or via agricultural techniques. Non-limitingexamples of renewable resources include plants (e.g., sugar cane, beets,corn, potatoes, citrus fruit, woody plants, lignocellulose,hemicellulose, cellulosic waste), animals, fish, bacteria, fungi, andforestry products. These resources can be naturally occurring, hybrids,or genetically engineered organisms. Natural resources, such as crudeoil, coal, natural gas, and peat, which take longer than 100 years toform, are not considered renewable resources. Because at least part ofthe material of the invention is derived from a renewable resource,which can sequester carbon dioxide, use of the material can reduceglobal warming potential and fossil fuel consumption.

As used herein, the term “bio-based content” refers to the amount ofcarbon from a renewable resource in a material as a percent of theweight (mass) of the total organic carbon in the material, as determinedby ASTM D6866-10 Method B.

As used herein, the term “petroleum-based” material refers to a materialthat is produced from fossil material, such as petroleum, natural gas,coal, etc.

As used herein, the term “condensed phosphate” refers to any saltscontaining one or several P—O—P bonds generated by corner sharing of PO₄tetrahedra.

As used herein, the term “cyclophosphate” refers to any cyclic condensedphosphate constituted of two or more corner-sharing PO₄ tetrahedra.

As used herein, the term “monophosphate” or “orthophosphate” refers toany salt whose anionic entity, [PO_(4]) ³⁻, is composed of four oxygenatoms arranged in an almost regular tetrahedral array about a centralphosphorus atom.

As used herein, the term “oligophosphate” refers to any polyphosphatesthat contain five or less PO₄ units.

As used herein, the term “polyphosphate” refers to any condensedphosphates containing linear P—O—P linkages by corner sharing of PO₄tetrahedra leading to the formation of finite chains.

As used herein, the term “ultraphosphate” refers to any condensedphosphate where at least two PO₄ tetrahedra of the anionic entity sharethree of their corners with the adjacent ones.

As used herein, the term “cation” refers to any atom or group ofcovalently-bonded atoms having a positive charge.

As used herein, the term “monovalent cation” refers to any cation with apositive charge of +1.

As used herein, the term “polyvalent cation” refers to any cation with apositive charge equal or greater than +2.

As used herein, the term “anion” refers to any atom or group ofcovalently-bonded atoms having a negative charge.

As used herein, the term “heteropolyanion” refers to any anion withcovalently bonded XO_(p) and YO_(r) polyhedra, and thus includes X—O—Yand possibly X—O—X and Y—O—Y bonds, wherein X and Y represent any atoms,and wherein p and r are any positive integers.

As used herein, the term “heteropolyphosphate” refers to anyheteropolyanion, wherein X represents phosphorus (P) and Y representsany other atom.

As used herein, the term “phosphate adduct” refers to any compound withone or more phosphate anions and one or more non-phosphate anions thatare not covalently linked.

As used herein, the terms “LA” refers to lactic acid, “AA” refers toacrylic acid, “AcH” refers to acetaldehyde, and “PA” refers to propionicacid.

As used herein, the term “particle span” refers to a statisticalrepresentation of a given particle sample and is equal to(D_(v,0.90)−D_(v,0.10))/D_(v,0.50). The term “median particle size” orD_(v,0.050) refers to the diameter of a particle below which 50% of thetotal volume of particles lies. Further, D_(v,0.10) refers to theparticle size that separates the particle sample at the 10% by volumefraction and D_(v,0.90), is the particle size that separates theparticle sample at the 90% by volume fraction.

As used herein, the term “conversion” in % is defined as[hydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof flow rate in (mol/min)—hydroxypropionic acid, hydroxypropionicacid derivatives, or mixtures thereof flow rate out(mol/min)]/[hydroxypropionic acid, hydroxypropionic acid derivatives, ormixtures thereof flow rate in (mol/min)]*100. For the purposes of thisinvention, the term “conversion” means molar conversion, unlessotherwise noted.

As used herein, the term “yield” in % is defined as [product flow rateout (mol/min)/hydroxypropionic acid, hydroxypropionic acid derivatives,or mixtures thereof flow rate in (mol/min)]*100. For the purposes ofthis invention, the term “yield” means molar yield, unless otherwisenoted.

As used herein, the term “selectivity” in % is defined as[Yield/Conversion]*100. For the purposes of this invention, the term“selectivity” means molar selectivity, unless otherwise noted.

As used herein, the term “total flow rate out” in mol/min and forhydroxypropionic acid is defined as: (2/3)*[C2 flow rate out(mol/min)]+[C3 flow rate out (mol/min)]+(2/3)*[acetaldehyde flow rateout (mol/min)]+(4/3)*[C4 flow rate out (mol/min)]+[hydroxypropionic acidflow rate out (mol/min)]+[pyruvic acid flow rate out(mol/min)]+(2/3)*[acetic acid flow rate out (mol/min)]+[1,2-propanediolflow rate out (mol/min)]+[propionic acid flow rate out(mol/min)]+[acrylic acid flow rate out(mol/min)]+(5/3)*[2,3-pentanedione flow rate out(mol/min)]+(1/3)*[carbon monoxide flow rate out (mol/min)]+(1/3)*[carbondioxide flow rate out (mol/min)]. If a hydroxypropionic acid derivativeis used instead of hydroxypropionic acid, the above formula needs to beadjusted according to the number of carbon atoms in the hydroxypropionicacid derivative.

As used herein, the term “C2” means ethane and ethylene.

As used herein, the term “C3” means propane and propylene.

As used herein, the term “C4” means butane and butenes.

As used herein, the term “total molar balance” or “TMB” in % is definedas [total flow rate out (mol/min)/hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof flow rate in(mol/min)]*100.

As used herein, the term “the acrylic acid yield was corrected for TMB”is defined as [acrylic acid yield/total molar balance]*100, to accountfor slightly higher flows in the reactor.

As used herein, the term “Gas Hourly Space Velocity” or “GHSV” in h⁻¹ isdefined as [Total gas flow rate (mL/min)/catalyst bed volume (mL)]/60.The total gas flow rate is calculated under Standard Temperature andPressure conditions (STP; 0° C. and 1 atm).

As used herein, the term “Liquid Hourly Space Velocity” or “LHSV” in h⁻¹is defined as [Total liquid flow rate (mL/min)/catalyst bed volume(mL)]/60.

II Poly(Acrylic Acid) and its Preparation Methods

Unexpectedly it has been found that bio-based glacial acrylic acid,acrylic acid derivatives, or mixtures thereof can be polymerized toproduce poly(acrylic acid) or superabsorbent polymer using processesthat are similar to those used in producing poly(acrylic acid) orsuperabsorbent polymer from petroleum-derived glacial acrylic acid,acrylic acid derivatives, or mixtures thereof. Although the impuritiesthat are present in bio-based acrylic acid, acrylic acid derivatives, ormixtures thereof are different than those present in the petroleum-basedglacial acrylic acid, acrylic acid derivatives, or mixtures thereof, thesame processes that are used to polymerize the petroleum-based glacialacrylic acid, acrylic acid derivatives, or mixtures thereof (e.g.processes for superabsorbent polymer disclosed in U.S. Pat. No.7,307,132 (issued in 2007) and U.S. Patent Applications 2009/0275470,2011/0306732, 2011/0313113, and 2012/0091392; all incorporated herein byreference) can be used to polymerize bio-based glacial acrylic acid,acrylic acid derivatives, or mixtures thereof.

In one embodiment, a superabsorbent polymer composition is provided andis produced from an acrylic composition, wherein the acrylic compositioncomprises an acrylic acid composition, wherein the acrylic acidcomposition consists of acrylic acid, acrylic acid derivatives, ormixtures thereof, wherein the acrylic acid composition comprises atleast about 98 wt % acrylic acid, acrylic acid derivatives, or mixturesthereof, and wherein a portion of the remaining impurities in theacrylic acid composition is hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof.

The acrylic composition comprises the acrylic acid composition andoptionally other materials, such as, by way of example and notlimitation, water, other solvents, or mixtures thereof.

Hydroxypropionic acid can be 3-hydroxypropionic acid, 2-hydroxypropionicacid (also called, lactic acid), 2-methyl hydroxypropionic acid, ormixtures thereof. Derivatives of hydroxypropionic acid can be metal orammonium salts of hydroxypropionic acid, alkyl esters ofhydroxypropionic acid, alkyl esters of 2-methyl hydroxypropionic acid,cyclic di-esters of hydroxypropionic acid, hydroxypropionic acidanhydride, or a mixture thereof. Non-limiting examples of metal salts ofhydroxypropionic acid are sodium hydroxypropionate, potassiumhydroxypropionate, and calcium hydroxypropionate. Non-limiting examplesof alkyl esters of hydroxypropionic acid are methyl hydroxypropionate,ethyl hydroxypropionate, butyl hydroxypropionate, 2-ethylhexylhydroxypropionate, or mixtures thereof. A non-limiting example of cyclicdi-esters of hydroxypropionic acid is dilactide.

In one embodiment, the hydroxypropionic acid is lactic acid or 2-methyllactic acid. In another embodiment, the hydroxypropionic acid is lacticacid. Lactic acid can be L-lactic acid, D-lactic acid, or mixturesthereof. In one embodiment, the hydroxypropionic acid, hydroxypropionicacid derivatives, or mixtures thereof in the impurities in the glacialacrylic acid composition are lactic acid, lactic acid derivatives, ormixtures thereof.

The acrylic acid derivatives can be acrylic acid oligomers, metal orammonium salts of monomeric acrylic acid, metal or ammonium salts ofacrylic acid oligomers, or mixtures thereof. Non-limiting examples ofmetal salts of acrylic acid are sodium acrylate and potassium acrylate.Non-limiting examples of alkyl esters of acrylic acid are methyllactate, ethyl lactate, or mixtures thereof.

The acrylic acid, acrylic acid derivatives, or mixtures thereof can bemade from renewable resources or materials. Non-limiting examples ofrenewable resources or materials are hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof; glycerin; carbonmonoxide and ethylene oxide; carbon dioxide and ethylene; and crotonicacid. In one embodiment, the renewable resources or materials arehydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof. In another embodiment, the renewable resources or materials arelactic acid, lactic acid derivatives, or mixtures thereof. In yetanother embodiment, the renewable resource or material is lactic acid.

In one embodiment, the superabsorbent polymer composition is produced bythe steps comprising: a) preparing a pre-polymerization solutioncontaining: (i) the acrylic composition, and (ii) a solvent; andwherein, the pH of the pre-polymerization solution is less than about 6;b) combining an initiator with the pre-polymerization solution toproduce a polymerization mixture; c) polymerizing the polymerizationmixture to produce a gel; and d) drying the gel to produce thesuperabsorbent polymer composition.

In another embodiment, the superabsorbent polymer composition isproduced by the steps comprising: a) preparing a pre-polymerizationsolution comprising: (i) the acrylic composition, and (ii) a solvent; b)mixing a base into the pre-polymerization solution to form a partiallyneutralized acrylic acid solution, and wherein, the pH of the partiallyneutralized acrylic acid solution is less than about 6; c) combining aninitiator with the partially neutralized acrylic acid solution toproduce a polymerization mixture; d) polymerizing the polymerizationmixture to produce a gel; and e) drying the gel to produce thesuperabsorbent polymer composition.

In one embodiment, the superabsorbent polymer composition is produced bythe steps comprising: a) preparing a pre-polymerization solutioncontaining: (i) the acrylic composition, and (ii) a solvent; andwherein, the pH of the pre-polymerization solution is less than about 6;b) combining an initiator with the pre-polymerization solution toproduce a polymerization mixture; c) polymerizing the polymerizationmixture to produce a gel; d) adding a crosslinking agent to the gel toproduce a crosslinked surface polymer; and e) drying the crosslinkedsurface polymer to produce the superabsorbent polymer composition.

In another embodiment, the superabsorbent polymer composition isproduced by the steps comprising: a) preparing a pre-polymerizationsolution comprising: (i) the acrylic composition, and (ii) a solvent; b)mixing a base into the pre-polymerization solution to form a partiallyneutralized acrylic acid solution, and wherein, the pH of the partiallyneutralized acrylic acid solution is less than about 6; c) combining aninitiator with the partially neutralized acrylic acid solution toproduce a polymerization mixture; d) polymerizing the polymerizationmixture to produce a gel; e) adding a crosslinking agent to the gel toproduce a crosslinked surface polymer; and f) drying the crosslinkedsurface polymer to produce the superabsorbent polymer composition.

In another embodiment, the superabsorbent polymer composition isproduced by the steps comprising: a) preparing a pre-polymerizationsolution comprising: glacial acrylic acid, methylene bis-acrylamide, andwater; b) mixing sodium hydroxide into the pre-polymerization solutionto form a partially neutralized acrylic acid solution; c) combining2,2′-azobis(2-methylpropionamidine)dihydrochloride with the partiallyneutralized acrylic acid solution to produce a polymerization mixture;d) polymerizing the polymerization mixture using UV light to produce agel; and e) drying the gel to produce the superabsorbent polymercomposition.

In one embodiment, the solvent of the pre-polymerization solution isselected from the group comprising water, organic solvents, and mixturesthereof. In yet another embodiment, the solvent of thepre-polymerization solution is water. In another embodiment, the pH ofthe pre-polymerization solution is between about 3 and about 5. Inanother embodiment, the pH of the partially neutralized acrylic acidsolution is between about 3 and about 5.

In another embodiment, the amount of the acrylic acid composition in thepre-polymerization solution is from about 5 wt % to about 95 wt %. Inanother embodiment, the amount of water in the pre-polymerizationsolution is from about 5 wt % to about 95 wt %. In yet anotherembodiment, the pre-polymerization solution further comprises adispersing aid. In one embodiment, the dispersing aid is carboxymethylcellulose (CMC).

In another embodiment, the pre-polymerization solution further comprisesa crosslinking agent. In yet another embodiment, the crosslinking agentis present in an amount of less than about 10 wt %, based on the totalamount of said acrylic acid composition in said pre-polymerizationsolution. In one embodiment, the crosslinking agent is selected from thegroup consisting of di- or poly-functional monomers, having two or moregroups that can be polymerized, such as N,N′-methylenebisacrylamide,trimethylolpropane triacrylate, ethylene glycol di(meth)acrylate, ortriallylamine, and other organic crosslinking agents that may beapparent to those having ordinary skills in the art.

In one embodiment, the initiator is an amount from about 0.01% wt % toabout 10 wt %, based on the total amount of the acrylic acid compositionin the pre-polymerization solution. In another embodiment, the initiatorcan be added as a solid or in combination with an initiator solvent,wherein the initiator and initiator solvent are forming a liquidsolution or dispersion. A non-limiting example of the initiator solventis water. Non-limiting examples of initiators are chemical compoundsselected from the group comprising hydroperoxides, hydrogen peroxide,organic peroxides, azo compounds, persulfates, other redox initiators,and mixtures thereof. Non-limiting examples of hydroperoxides aretert-butyl hydroperoxide and cumene hydroperoxide. Non-limiting examplesof organic peroxides are acetylacetone peroxide, methyl ethyl ketoneperoxide, tert-amyl perpivalate, tert-butyl perpivalate, tert-butylperneohexanoate, tert-butyl perisobutyrate, tert-butylper-2-ethylhexanoate, tert-butyl perisononanoate, tert-butyl permaleate,tert-butyl perbenzoate, di(2-ethylhexyl) peroxydicarbonate, dicyclohexylperoxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate,dimyristyl peroxydicarbonate, diacetyl peroxydicarbonate, allylperesters, cumyl peroxyneodecanoate, tert-butylper-3,5,5-tri-methylhexanoate, acetylcyclohexylsulfonyl peroxide,dilauryl peroxide, dibenzoyl peroxide, and tert-amyl perneodecanoate.Non-limiting examples of azo compounds are 2,2′-azobisisobutyronitrile,2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(4-methoxy-2,4-dimethyl-valeronitrile),2,2′-azobis-{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}dihydrochloride,2,2′-azobis-(2-amidinopropane) dihydrochloride,2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, and2,2′-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride.Non-limiting examples of persulfates are sodium peroxodisulfate,potassium peroxodisulfate and ammonium peroxodisulfate. In anotherembodiment, a mixture of two or more initiators is used.

In another embodiment, a polymerization catalyst can be used. Anon-limiting example of a polymerization catalyst is TMEDA(N,N,N′,N′-tetramethylethylenediamine). Polymerization methods toprepare the superabsorbent polymer composition can include free radical,ring-opening, condensation, anionic, cationic, or irradiationtechniques. The polymerization rate can be controlled through theidentity and amount of initiators and the polymerization temperature.The polymerization of the acrylic acid composition can be highlyexothermic, and hence, in one embodiment, the polymerization solutioncan be cooled during polymerization.

In one embodiment, the partially neutralized acrylic acid solutioncomprises at least about 20 mol % of an acrylic acid salt, based on thetotal amount of the acrylic acid composition, and wherein the acrylicacid salt is produced in the mixing step. In another embodiment, thepartially neutralized acrylic acid solution comprises at least about 40mol % of an acrylic acid salt, based on the total amount of the acrylicacid composition, and wherein the acrylic acid salt is produced in themixing step. In another embodiment, the partially neutralized acrylicacid solution comprises at least about 60 mol % of an acrylic acid salt,based on the total amount of the acrylic acid composition, and whereinthe acrylic acid salt is produced in the mixing step. In anotherembodiment, the partially neutralized acrylic acid solution comprises atleast about 80 mol % of an acrylic acid salt, based on the total amountof the acrylic acid composition, and wherein the acrylic acid salt isproduced in the mixing step.

In one embodiment, at least about 20 mol % of the acrylic acidcomposition in the partially neutralized acrylic acid solution containsa carboxylate group with a cationic counter ion. In another embodiment,at least about 40 mol % of the acrylic acid composition in the partiallyneutralized acrylic acid solution contains a carboxylate group with acationic counter ion. In another embodiment, at least about 60 mol % ofthe acrylic acid composition in the partially neutralized acrylic acidsolution contains a carboxylate group with a cationic counter ion. Inanother embodiment, at least about 80 mol % of the acrylic acidcomposition in the partially neutralized acrylic acid solution containsa carboxylate group with a cationic counter ion. Non-limiting examplesof bases are sodium hydroxide and potassium hydroxide.

In another embodiment, a crosslinking agent is added to the gel afterthe polymerization is completed to produce a crosslinked surfacepolymer, and the crosslinked surface polymer is dried to produce thesuperabsorbent polymer composition. Surface crosslinking of theinitially formed polymers is a preferred process for obtainingsuperabsorbent polymers having relatively high performance underpressure (PUP) capacity, porosity and permeability. Non-limitingexamples of processes to produce a crosslinked surface polymer are:those where a) a di- or poly-functional reagent (s) capable of reactingwith existing functional groups within the superabsorbent polymer isapplied to the surface of the polymer; b) a di- or poly-functionalreagent that is capable of reacting with other added reagents andpossibly existing functional groups within the absorbent polymer such asto increase the level of crosslinking at the surface is applied to thesurface; c) additional reaction (s) is induced amongst existingcomponents within the superabsorbent polymer, such as to generate ahigher level of crosslinking at or near the surface; among others thatmay be apparent to those having skill in the art.

In one embodiment, the superabsorbent polymer composition comprises: a)a cation-exchange absorbent polymer prepared from an acryliccomposition, wherein the acrylic composition comprises an acrylic acidcomposition, wherein the acrylic acid composition consists of acrylicacid, acrylic acid derivatives, or mixtures thereof, wherein the acrylicacid composition comprises at least about 98 wt % acrylic acid, acrylicacid derivatives, or mixtures thereof, and wherein a portion of theremaining impurities in the acrylic acid composition is hydroxypropionicacid, hydroxypropionic acid derivatives, or mixtures thereof; and b) ananion-exchange absorbent polymer, wherein the ion-exchange capacity ofthe anion-exchange absorbent polymer is at least about 15 meq/g.

In one embodiment, the hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof in the impurities in the glacialacrylic acid composition are lactic acid, lactic acid derivatives, ormixtures thereof.

In another embodiment, the cation-exchange absorbent polymer is fromabout 80% to about 100% in the un-neutralized acid form and theanion-exchange absorbent polymer is from about 80% to about 100% in theun-neutralized base form. In another embodiment, the anion-exchangeabsorbent polymer is prepared from a monomer selected from the groupconsisting of ethylenimine, allylamine, diallylamine, 4-aminobutene,alkyl oxazolines, vinylformamide, 5-aminopentene, carbodiimides,formaldazine, and melamine; a secondary amine derivative of any of theforegoing; a tertiary amine derivative of any of the foregoing; andmixtures therefore. In another embodiment, the anion-exchange absorbentpolymer is prepared from a monomer selected from the group consisting ofethylenimine, allylamine, diallylamine, and mixtures thereof.

In another embodiment, the superabsorbent polymer composition comprises:a) the anion-exchange absorbent polymer selected from the groupconsisting of poly(ethylenimine); poly(allylamine); and mixturesthereof; and b) the cation-exchange polymer is a homopolymer orcopolymer of the acrylic acid prepared from an acrylic composition,wherein the acrylic composition comprises an acrylic acid composition,wherein the acrylic acid composition consists of acrylic acid, acrylicacid derivatives, or mixtures thereof, wherein the acrylic acidcomposition comprises at least about 98 wt % acrylic acid, acrylic acidderivatives, or mixtures thereof, and wherein a portion of the remainingimpurities in the acrylic acid composition is hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof. In anotherembodiment, the cation-exchange absorbent polymer is homogenouslycrosslinked.

In one embodiment, the bio-based content of the acrylic acid compositionis greater than about 3%. In another embodiment, the bio-based contentof the acrylic acid composition is greater than 30%. In yet anotherembodiment, the bio-based content of the acrylic acid composition isgreater than about 90%. In one embodiment, the bio-based content of thesuperabsorbent polymer composition is greater than about 3%. In anotherembodiment, the bio-based content of the superabsorbent polymercomposition is greater than 30%. In yet another embodiment, thebio-based content of the superabsorbent polymer composition is greaterthan about 90%.

In one embodiment, the superabsorbent polymer composition has a cylinderretention capacity (CRC) between about 20 g/g and about 45 g/g. Inanother embodiment, the superabsorbent polymer composition has acylinder retention capacity (CRC) between about 25 g/g and about 40 g/g.In yet another embodiment, the superabsorbent polymer composition has acylinder retention capacity (CRC) between about 30 g/g and about 35 g/g.

In one embodiment, the superabsorbent polymer composition has anextractables value from about 0 wt % to about 20 wt %. In anotherembodiment, the superabsorbent polymer composition has an extractablesvalue from about 3 wt % to about 15 wt %. In yet another embodiment, thesuperabsorbent polymer composition has an extractables value from about5 wt % to about 10 wt %.

In one embodiment, the superabsorbent polymer composition has absorptionagainst pressure (AAP) between about 15 g/g and about 40 g/g. In anotherembodiment, the superabsorbent polymer composition has absorptionagainst pressure (AAP) between about 20 g/g and about 35 g/g. In yetanother embodiment, the superabsorbent polymer composition hasabsorption against pressure (AAP) between about 25 g/g and about 30 g/g.

In one embodiment, the amount of residual monomers in the superabsorbentpolymer composition is about 500 ppm or less.

In one embodiment, an absorbent article is provided and is selected fromadult incontinence garments, infant diapers, and feminine hygienearticles, and produced from an acrylic composition, wherein the acryliccomposition comprises an acrylic acid composition, wherein the acrylicacid composition consists of acrylic acid, acrylic acid derivatives, ormixtures thereof, wherein the acrylic acid composition comprises atleast about 98 wt % acrylic acid, acrylic acid derivatives, or mixturesthereof, and wherein a portion of the remaining impurities in theacrylic acid composition is hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof.

In another embodiment, an absorbent article is provided having opposinglongitudinal edges and comprising: a) a top sheet; b) a back sheetjoined with the top sheet; and c) an absorbent core disposed between thetop sheet and the back sheet, and wherein, the absorbent core comprisesa superabsorbent polymer composition produced from an acryliccomposition, wherein the acrylic composition comprises an acrylic acidcomposition, wherein the acrylic acid composition consists of acrylicacid, acrylic acid derivatives, or mixtures thereof, wherein the acrylicacid composition comprises at least about 98 wt % acrylic acid, acrylicacid derivatives, or mixtures thereof, and wherein a portion of theremaining impurities in the acrylic acid composition is hydroxypropionicacid, hydroxypropionic acid derivatives, or mixtures thereof.

In one embodiment, an absorbent member comprises an agglomerate of: a)particulate superabsorbent polymer composition prepared from an acryliccomposition, wherein the acrylic composition comprises an acrylic acidcomposition, wherein the acrylic acid composition consists of acrylicacid, acrylic acid derivatives, or mixtures thereof, wherein the acrylicacid composition comprises at least about 98 wt % acrylic acid, acrylicacid derivatives, or mixtures thereof, and wherein a portion of theremaining impurities in the acrylic acid composition is hydroxypropionicacid, hydroxypropionic acid derivatives, or mixtures thereof; and b)particulate high surface area open-celled hydrophilic foam, wherein thefoam, in combination with the superabsorbent polymer composition,provides the absorbent member with high capillary sorption absorbentcapacity. The absorbent member is useful in the containment (e.g.storage) of body liquid fluids such as urine. As used herein, the term“agglomerate” refers to a unitary combination of particulate materialsthat is not easily separable, i.e. the agglomerate does notsubstantially separate into its component particles as a result ofnormal manufacturing, normal shipping, and/or normal use. High surfacearea foams useful herein are those that are relatively open-celled, i.e.many of the individual cells of the foam are in unobstructedcommunication with adjoining cells, allowing liquid transfer from onecell to the other within the foam structure. In addition to beingopen-celled, these high surface area foams are sufficiently hydrophilicto permit the foam to absorb aqueous liquids.

In another embodiment, the high surface area open-celled hydrophilicfoam is obtained by polymerizing a high internal phase water-in-oilemulsion (HIPE). In another embodiment, a hydratable, and preferablyhygroscopic or deliquescent, water soluble inorganic salt isincorporated into the HIPE. Non-limiting examples of water solubleinorganic salts are alkaline earth metal salts, such as calciumchloride. In one embodiment, the agglomerate comprises from about 1 wt %to about 98 wt % high surface area open-celled hydrophilic foam, basedon the total weight of the agglomerate. In another embodiment, theagglomerate comprises from about 15 wt % to about 85 wt % high surfacearea open-celled hydrophilic foam, based on the total weight of theagglomerate. In yet another embodiment, the agglomerate comprises fromabout 30 wt % to about 40 wt % high surface area open-celled hydrophilicfoam, based on the total weight of the agglomerate.

In another embodiment, a poly(acrylic acid) composition is provided andis produced from an acrylic composition, wherein the acrylic compositioncomprises an acrylic acid composition, wherein the acrylic acidcomposition consists of acrylic acid, acrylic acid derivatives, ormixtures thereof, wherein the acrylic acid composition comprises atleast about 98 wt % acrylic acid, acrylic acid derivatives, or mixturesthereof, and wherein a portion of the remaining impurities in theacrylic acid composition is hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof.

III Catalysts for the Conversion of Hydroxypropionic Acid or itsDerivatives to Acrylic Acid or its Derivatives

In one embodiment, the acrylic acid composition is produced fromhydroxypropionic acid, hydroxypropionic acid derivatives, and mixturesthereof by using a catalyst. In another embodiment, the catalystcomprises: (a) at least one condensed phosphate anion selected from thegroup consisting of formulae (I), (II), and (III),[P_(n)O_(3n+1)]^((n+2))−  (I)[P_(n)O_(3n)]^(n−)  (II)[P_((2m+n))O_((5m+3n))]^(n−)  (III)wherein n is at least 2 and m is at least 1, and (b) at least twodifferent cations, wherein the catalyst is essentially neutrallycharged, and further, wherein the molar ratio of phosphorus to the atleast two different cations is between about 0.7 and about 1.7.

The anions defined by formulae (I), (II), and (III) are also referred toas polyphosphates (or oligophosphates), cyclophosphates, andultraphosphates, respectively.

In another embodiment, the catalyst comprises: (a) at least onecondensed phosphate anion selected from the group consisting of formulae(I) and (II),[P_(n)O_(3n+1)]^((n+2)−)  (I)[P_(n)O_(3n)]^(n−)  (II)wherein n is at least 2, and (b) at least two different cations, whereinthe catalyst is essentially neutrally charged, and further, wherein themolar ratio of phosphorus to the at least two different cations isbetween about 0.7 and about 1.7.

The cations can be monovalent or polyvalent. In one embodiment, onecation is monovalent and the other cation is polyvalent. In anotherembodiment, the polyvalent cation is selected from the group consistingof divalent cations, trivalent cations, tetravalent cations, pentavalentcations, and mixtures thereof. Non-limiting examples of monovalentcations are H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ag⁺, Rb⁺, Tl⁺, and mixturesthereof. In one embodiment, the monovalent cation is selected from thegroup consisting of Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and mixtures thereof; inanother embodiment, the monovalent cation is Na⁺ or K⁺; and in yetanother embodiment, the monovalent cation is K⁺. Non-limiting examplesof polyvalent cations are cations of the alkaline earth metals (i.e.,Be, Mg, Ca, Sr, Ba, and Ra), transition metals (e.g. Y, Ti, Zr, V, Nb,Cr, Mo, Mn, Re, Fe, Ru, Co, Rh, Ni, Pd, Pt, Cu, Ag, and Au), poor metals(e.g. Zn, Ga, Si, Ge, B, Al, In, Sb, Sn, Bi, and Pb), lanthanides (e.g.La and Ce), and actinides (e.g. Ac and Th). In one embodiment, thepolyvalent cation is selected from the group consisting of Be²⁺, Mg²⁺,Ca²⁺, Sr²⁺, Ba²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Sn²⁺, Pb²⁺,Ti³⁺, Cr³⁺, Mn³⁺, Fe³⁺, Al³⁺, Ga³⁺, Y³⁺, In³⁺, Sb³⁺, Bi³⁺, Si⁴⁺, Ti⁴⁺,V⁴⁺, Ge⁴⁺, Mo⁴⁺, Pt⁴⁺, V⁵⁺, Nb⁵⁺, Sb⁵⁺, and mixtures thereof. In oneembodiment, the polyvalent cation is selected from the group consistingof Ca²⁺, Ba²⁺, Cu²⁺, Mn²⁺, Mn³⁺, and mixtures thereof; in anotherembodiment, the polyvalent cation is selected from the group consistingof Ca²⁺, Ba²⁺, Mn³⁺, and mixtures thereof; and in yet anotherembodiment, the polyvalent cation is Ba²⁺.

The catalyst can include cations: (a) H⁺, Li⁺, Na⁺, K^(+t), Rb⁺, Cs⁺, ormixtures thereof; and (b) Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mn²⁺, Fe²⁺,Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Sn₂₊, Pb²⁺, Ti³⁺, Cr³⁺, Mn³⁺, Fe³⁺, Al³⁺,Ga³⁺, Y³⁺, In³⁺, Sb³⁺, Bi³⁺, Si⁴⁺, Ti⁴⁺, V⁴⁺, Ge⁴⁺, Mo⁴⁺, Pt⁴⁺, V⁵⁺,Nb⁵⁺, Sb⁵⁺, or mixtures thereof. In one embodiment the catalystcomprises Li⁺, Na⁺, or K⁺ as monovalent cation, and Ca²⁺, Ba²⁺, or Mn³⁺as polyvalent cation; in another embodiment, the catalyst comprises Na⁺or K⁺ as monovalent cation, and Ca²⁺ or Ba²⁺ as polyvalent cation; andin yet another embodiment, the catalyst comprises K⁺ as the monovalentcation and Ba²⁺ as the polyvalent cation.

In one embodiment, the catalyst comprises Ba_(2-x-s)K_(2x)H_(2s)P₂O₇ and(KPO₃)_(n), wherein x and s are greater or equal to 0 and less thanabout 0.5 and n is a positive integer. In another embodiment, thecatalyst comprises Ca_(2-x-s)K_(2x)H_(2s)P₂O₇ and (KPO₃)_(n), wherein xand s are greater or equal to 0 and less than about 0.5 and n is apositive integer. In yet another embodiment, the catalyst comprisesMn_(1-x-s)K_(1+3x)H_(3s)P₂O₇ or Mn_(1-x-s)K₂₊₂H_(2s)P₂O₇ and (KPO₃)_(n)wherein x and s are greater or equal to 0 and less than about 0.5 and nis a positive integer. In another embodiment, the catalyst comprises anyblend of Ba_(2-x-s)K_(2x)H_(2s)P₂O₇, Ca_(2-x-s)K_(2s)P₂O₇,Mn_(1-x-s)K_(1+3x)H_(3s)P₂O₇ or Mn_(1-x-s)K_(2+2x)H_(2s)P₂O₇; and(KPO₃)_(n), wherein x and s are greater or equal to 0 and less thanabout 0.5 and n is a positive integer.

In one embodiment, the molar ratio of phosphorus to the cations in thecatalyst is between about 0.7 and about 1.7; in another embodiment, themolar ratio of phosphorus to the cations in the catalyst is betweenabout 0.8 and about 1.3; and in yet another embodiment, the molar ratioof phosphorus to the cations in the catalyst is about 1.

In one embodiment, the catalyst comprises: (a) at least two differentcondensed phosphate anions selected from the group consisting offormulae (I), (II), and (III),[P_(n)O_(3n+1)]^((n+2))−  (I)[P_(n)O_(3n)]^(n−)  (II)[P_((2m+n))O_((5m+3n)]) ^(n−)  (III)wherein n is at least 2 and m is at least 1, and (b) one cation, whereinthe catalyst is essentially neutrally charged, and further, wherein themolar ratio of phosphorus to the cation is between about 0.5 and about4.0. In another embodiment, the molar ratio of phosphorus to the cationis between about t/2 and about t, wherein t is the charge of the cation.

The catalyst can include an inert support that is constructed of amaterial comprising silicates, aluminates, carbons, metal oxides, andmixtures thereof. Alternatively, the carrier is inert relative to thereaction mixture expected to contact the catalyst. In the context of thereactions expressly described herein, in one embodiment the carrier is alow surface area silica or zirconia. When present, the carrierrepresents an amount of about 5 wt % to about 98 wt %, based on thetotal weight of the catalyst. Generally, a catalyst that includes aninert support can be made by one of two exemplary methods: impregnationor co-precipitation. In the impregnation method, a suspension of thesolid inert support is treated with a solution of a pre-catalyst, andthe resulting material is then activated under conditions that willconvert the pre-catalyst to a more active state. In the co-precipitationmethod, a homogenous solution of the catalyst ingredients isprecipitated by the addition of additional ingredients.

In another embodiment, the catalyst can be sulfate salts; phosphatesalts; mixtures of sulfate and phosphate salts; bases; zeolites ormodified zeolites; metal oxides or modified metal oxides; supercriticalwater, or mixtures thereof.

IV Catalyst Preparation Methods

In one embodiment, the method of preparing the catalyst includes mixingand heating at least two different phosphorus containing compounds,wherein each the compound is described by one of the formulae (IV) to(XXV), or any of the hydrated forms of the formulae:M^(I) _(y)(H_(3−y)PO₄)  (IV)M^(II) _(y)(H_(3−y)PO₄)₂  (V)M^(III) _(y)(H_(3−y)PO₄)₃  (VI)M^(IV) _(y)(H_(3−y)PO₄)₄  (VII)(NH₄)_(y)(H_(3−y)PO₄)  (VIII)M^(II) _(a)(OH)_(b)(PO₄)_(c)  (IX)M^(III) _(d)(OH)_(c)(PO₄)_(f)  (X)M^(II)M^(I)PO₄  (XI)M^(III)M^(I) ₃(PO₄)₂  (XII)M^(IV) ₂M^(I)PO₄)₂  (XIII)M^(I) _(z)H_(4−z)P₂O₇  (XIV)M^(II) _(v)H_((4−2v))P₂O₇  (XV)M^(IV)P₂O₇  ((XVI)(NH₄)_(z)H_(4−z)P₂O₇  (XVII)M^(III)M^(I)P₂O₇  (XVIII)M^(I)H_(w)(PO₃)_((1+w))  (XIX)M^(II)H_(w)(PO₃)_((2+w))  (XX)M^(III)H_(w)(PO₃)_((3+w))  (XXI)M^(IV)H_(w)(PO₃)_((4+w))  (XXII)M^(II) _(g)M^(I) _(h)(PO₃)_(i)  (XXIII)M^(III) _(j)M^(I) _(k)(PO₃)_(l)  (XXIV)P₂O₅  (XXV)wherein M^(I) is a monovalent cation; wherein M^(II) is a divalentcation; wherein M^(III) is a trivalent cation; wherein M^(IV) is atetravalent cation; wherein y is 0, 1, 2, or 3; wherein z is 0, 1, 2, 3,or 4; wherein v is 0, 1, or 2; wherein w is 0 or any positive integer;and wherein a, b, c, d, e, f, g, h, i, j, k, and l are any positiveintegers, such that the equations: 2a=b+3c, 3d=e+3f, i=2g+h, and 1=3j+kare satisfied.

In one embodiment, the catalyst is prepared by mixing and heating one ormore phosphorus containing compounds of formula (IV), wherein y is equalto 1, and one or more phosphorus containing compounds of formula (V),wherein y is equal to 2. In another embodiment, the catalyst is preparedby mixing and heating M^(I)H₂PO₄ and M^(II)HPO₄. In one embodiment,M^(I) is K⁺ and M^(II) is Ca²⁺, i.e., the catalyst is prepared by mixingand heating KH₂PO₄ and CaHPO₄; or M^(I) is K and M^(II) is Ba²⁺, i.e.,the catalyst is prepared by mixing and heating KH₂PO₄ and BaHPO₄.

In one embodiment, the catalyst is prepared by mixing and heating one ormore phosphorus containing compound of formula (IV), wherein y is equalto 1, one or more phosphorus containing compounds of formula (XV),wherein v is equal to 2. In another embodiment, the catalyst is preparedby mixing and heating M^(I)H₂PO₄ and M^(II) ₂P₂O₇. In one embodiment,M^(I) is K⁺ and M^(II) is Ca²⁺, i.e., the catalyst is prepared by mixingand heating KH₂PO₄ and Ca₂P₂O₇; or M^(I) is K⁺ and M^(II) is Ba²⁺, i.e.,the catalyst is prepared by mixing and heating KH₂PO₄ and Ba₂P₂O₇.

In another embodiment, the molar ratio of phosphorus to the cations inthe catalyst is between about 0.7 and about 1.7; in yet anotherembodiment, the molar ratio of phosphorus to the cations in the catalystis between about 0.8 and about 1.3; and in another embodiment, the molarratio of phosphorus to the cations in the catalyst is about 1.

In another embodiment, the method of preparing the catalyst includesmixing and heating (a) at least one phosphorus containing compound,wherein each the compound is described by one of the formulae (IV) to(XXV), or any of the hydrated forms of the formulae:M^(I) _(y)(H_(3−y)PO₄)  (IV)M^(II) _(y)(H_(3−y)PO₄)₂  (V)M^(III) _(y)(H_(3−y)PO₄)₃  (VI)M^(IV) _(y)(H_(3−y)PO₄)₄  (VII)(NH₄)_(y)(H_(3−y)PO₄)  (VIII)M^(II) _(a)(OH)_(b)(PO₄)_(c)  (IX)M^(III) _(d)(OH)_(c)(PO₄)_(f)  (X)M^(II)M^(I)PO₄  (XI)M^(III)M^(I) ₃(PO₄)₂  (XII)M^(IV) ₂M^(I)PO₄)₃  (XIII)M^(I) _(z)H_(4−z)P₂O₇  (XIV)M^(II) _(v)H_((4−2v))P₂O₇  (XV)M^(IV)P₂O₇  ((XVI)(NH₄)_(z)H_(4−z)P₂O₇  (XVII)M^(III)M^(I)P₂O₇  (XVIII)M^(I)H_(w)(PO₃)_((1+w))  (XIX)M^(II)H_(w)(PO₃)_((2+w))  (XX)M^(III)H_(w)(PO₃)_((3+w))  (XXI)M^(IV)H_(w)(PO₃)_((4+w))  (XXII)M^(II) _(g)M^(I) _(h)(PO₃)_(i)  (XXIII)M^(III) _(j)M^(I) _(k)(PO₃)_(l)  (XXIV)P₂O₅  (XXV)wherein y is 0, 1, 2, or 3; wherein z is 0, 1, 2, 3, or 4; wherein v is0, 1, or 2; wherein w is 0 or any positive integer; and wherein a, b, c,d, e, f, g, h, i, j, k, and l are any positive integers, such that theequations: 2a=b+3c, 3d=e+3f, i=2g+h, and 1=3j+k are satisfied, and (b)at least one non-phosphorus containing compound selected from the groupconsisting of nitrate salts, carbonate salts, acetate salts, metaloxides, chloride salts, sulfate salts, and metal hydroxides, whereineach the compound is described by one of the formulae (XXVI) to (XL), orany of the hydrated forms of the formulae:M^(I)NO₃  (XXVI)M^(II)(NO₃)₂  (XXVII)M^(III)(NO₃)₃  (XXVIII)M^(I) ₂CO₃  (XXIX)M^(II) ₂CO₃  (XXX)M^(III) ₂(CO₃)₃  (XXXI)(CH₃COO)M^(I)  (XXXII)(CH₃COO)₂M^(II)  (XXXIII)(CH₃COO)₃M^(III)  (XXXIV)(CH₃COO)₄M^(IV)  (XXXV)M^(I) ₂O  (XXXVI)M^(II)O  (XXXVII)M^(III) ₂O₂  (XXXVIII)M^(IV)O₂  (XXXIX)M^(I)Cl  (XXXX)M^(II)Cl₂  (XXXXI)M^(III)Cl₃  (XXXXII)M^(IV)Cl₄  (XXXXIII)M^(I) ₂SO₄  (XXXXIV)M^(II)SO₄  (XXXXV)M^(III) ₂(SO₄)₃  (XXXXVI)M^(IV)(SO₄)₂  (XXXXVII)M^(I)OH  (XXXVIII)M^(II)(OH)₂  (XXXIX)M^(III)(OH)₃  (XL).

In another embodiment, the non-phosphorus containing compounds can beselected from the group consisting of carboxylic acid-derived salts,halide salts, metal acetylacetonates, and metal alkoxides.

In one embodiment of the present invention, the molar ratio ofphosphorus to the cations in the catalyst is between about 0.7 and about1.7; in another embodiment, the molar ratio of phosphorus to the cationsin the catalyst is between about 0.8 and about 1.3; and in yet anotherembodiment, the molar ratio of phosphorus to the cations in the catalystis about 1.

In another embodiment of the present invention, the catalyst is preparedby mixing and heating one or more phosphorus containing compounds offormulae (IV) to (XXV) or their hydrated forms, and one or more nitratesalts of formulae (XXVI) to (XXVIII) or their hydrated forms. In anotherembodiment of the present invention, the catalyst is prepared by mixingand heating one or more phosphorus containing compounds of formula (IV)and one or more nitrate salts of formula (XXVII). In a furtherembodiment of the present invention, the catalyst is prepared by mixingand heating a phosphorus containing compound of formula (IV) wherein yis equal to 2, a phosphorus containing compound of formula (IV) whereiny is equal to 0 (i.e., phosphoric acid), and a nitrate salt of formula(XXVII). In yet another embodiment of the present invention, thecatalyst is prepared by mixing and heating K₂HPO₄, H₃PO₄, and Ba(NO₃)₂.In yet another embodiment, the catalyst is prepared by mixing andheating K₂HPO₄, H₃PO₄, and Ca(NO₃)₂.

In one embodiment of the present invention, the catalyst is prepared bymixing and heating one or more phosphorus containing compounds offormula (IV) and one or more nitrate salts of formula (XXVIII). In afurther embodiment of the present invention, the catalyst is prepared bymixing and heating a phosphorus containing compound of formula (IV)wherein y is equal to 2, a phosphorus containing compound of formula(IV) wherein y is equal to 0 (i.e., phosphoric acid), and a nitrate saltof formula (XXVIII). In yet another embodiment of the present invention,the catalyst is prepared by mixing and heating K₂HPO₄, H₃PO₄, andMn(NO₃)₂.4H₂O.

In one embodiment of the present invention, the catalyst is prepared bymixing and heating one or more phosphorus containing compounds offormula (V) and one or more nitrate salts of formula (XXVI). In anotherembodiment of the present invention, the catalyst is prepared by mixingand heating a phosphorus containing compound of formula (V) wherein y isequal to 2, a phosphorus containing compound of formula (V) wherein y isequal to 0 (i.e., phosphoric acid), and a nitrate salt of formula(XXVI). In yet another embodiment of the present invention, the catalystis prepared by mixing and heating BaHPO₄, H₃PO₄, and KNO₃. In anotherembodiment, the catalyst is prepared by mixing and heating CaHPO₄,H₃PO₄, and KNO₃.

In one embodiment of this invention, the catalyst is prepared by mixingand heating one or more phosphorus containing compounds of formula (V),one or more phosphorus containing compounds of formula (XV), and one ormore nitrate salts of formula (XXVI). In a further embodiment of thisinvention, the catalyst is prepared by mixing and heating a phosphoruscontaining compound of formula (V), wherein y is equal to 0 (i.e.,phosphoric acid); a phosphorus containing compound of formula (XV),wherein v is equal to 2; and a nitrate salt of formula (XXVI). Inanother embodiment of the present invention, the catalyst is prepared bymixing and heating H₃PO₄, Ca₂P₂O₇, and KNO₃. In yet another embodiment,the catalyst is prepared by mixing and heating H₃PO₄, Ba₂P₂O₇, and KNO₃.

In another embodiment of this invention, the catalyst is prepared bymixing and heating one or more phosphorus containing compounds offormula (VI) and one or more nitrate salts of formula (XXVI). In anotherembodiment of this invention, the catalyst is prepared by mixing andheating a phosphorus containing compound of formula (VI), wherein y isequal to 3; a phosphorus containing compound of formula (VI), wherein yis equal to 0 (i.e., phosphoric acid); and a nitrate salt of formula(XXVI). In yet another embodiment of this invention, the catalyst isprepared by mixing and heating MnPO₄.qH₂O, H₃PO₄, and KNO₃.

In one embodiment of this invention, the catalyst is prepared by mixingand heating one or more phosphorus containing compounds of formula (IV),one or more phosphorus containing compounds of formula (IX), and one ormore nitrate salts of formula (XXVII). In another embodiment of thisinvention, the catalyst is prepared by mixing and heating a phosphoruscontaining compound of formula (IV), wherein y is equal to 2; aphosphorus containing compound of formula (IV), wherein y is equal to 0(i.e., phosphoric acid); a phosphorus containing compound of formula(IX), wherein a is equal to 2, b is equal to 1, and c is equal to 1; anda nitrate salt of formula (XXVII). In yet another embodiment of thisinvention, the catalyst is prepared by mixing and heating K₂HPO₄, H₃PO₄,Cu₂(OH)PO₄, and Ba(NO₃)₂.

In one embodiment of this invention, the catalyst is prepared by mixingand heating one or more phosphorus containing compounds of formula (V),one or more phosphorus containing compounds of formula (IX), and one ormore nitrate salts of formula (XXVI). In another embodiment of thisinvention, the catalyst is prepared by mixing and heating a phosphoruscontaining compound of formula (V), wherein y is equal to 3; aphosphorus containing compound of formula (V), wherein y is equal to 0(i.e., phosphoric acid); a phosphorus containing compound of formula(IX), wherein a is equal to 2, b is equal to 1, and c is equal to 1; anda nitrate salt of formula (XXVI). In yet another embodiment, thecatalyst is prepared by mixing and heating Ba₃(PO₄)₂, H₃PO₄, Cu₂(OH)PO₄,and KNO₃.

In one embodiment of the present invention, the catalyst is prepared bymixing and heating one or more phosphorus containing compounds describedby one of the formulae (IV) to (XXV) or any of the hydrated forms, andone or more carbonate salts described by one of the formulae (XXIX) to(XXXI) or any of the hydrated forms.

In one embodiment of the present invention, the catalyst is prepared bymixing and heating one or more phosphorus containing compounds describedby one of the formulae (IV) to (XXV) or any of the hydrated forms, andone or more acetate salts described by one of the formulae (XXXII) to(XXXV), any other organic acid-derived salts, or any of the hydratedforms.

In one embodiment of the present invention, the catalyst is prepared bymixing and heating one or more phosphorus containing compounds describedby one of the formulae (IV) to (XXV) or any of the hydrated forms, andone or more metal oxides described by one of the formulae (XXXVI) to(XXXIX) or any of the hydrated forms.

In one embodiment of the present invention, the catalyst is prepared bymixing and heating one or more phosphorus containing compounds describedby one of the formulae (IV) to (XXV) or any of the hydrated forms, andone or more chloride salts described by one of the formulae (XXXX) to(XXXXIII), any other halide salts, or any of the hydrated forms.

In one embodiment of the present invention, the catalyst is prepared bymixing and heating one or more phosphorus containing compounds describedby one of the formulae (IV) to (XXV) or any of the hydrated forms, andone or more sulfate salts described by one of the formulae (XXXXIV) to(XXXXVII) or any of the hydrated forms.

In one embodiment of the present invention, the catalyst is prepared bymixing and heating one or more phosphorus containing compounds describedby one of the formulae (IV) to (XXV) or any of the hydrated forms, andone or more hydroxides described by one of the formulae (XXXXVIII) to(XL) or any of the hydrated forms.

In one embodiment of the present invention, the catalyst is prepared bymixing and heating one or more phosphorus containing compounds offormulae (IV) to (XXV), and two or more non-phosphorus containingcompounds of formulae (XXVI) to (XL) or their hydrated forms.

In one embodiment, the molar ratio of phosphorus to the cations (i.e.,M^(I)+M^(II)+M^(III)+ . . . ) is between about 0.7 and about 1.7; inanother embodiment, the molar ratio of phosphorus to the cations (i.e.,M_(I)+M_(II)+M^(III)+ . . . ) is between about 0.8 and about 1.3, and inyet another embodiment, the molar ratio of phosphorus to the cations(i.e., M_(I)+M_(II)+M^(III)+ . . . ) is about 1. For example, in anembodiment when the catalyst includes potassium (K⁺) and barium (Ba²⁺),the molar ratio between phosphorus and the metals (K+Ba) is betweenabout 0.7 and about 1.7; and in another embodiment, the molar ratiobetween phosphorus and the metals (K+Ba) is about 1 about 1.

When the catalyst includes only two different cations, the molar ratiobetween cations is, in one embodiment, between about 1:50 and about50:1; and in another embodiment, the molar ratio between cations isbetween about 1:4 and about 4:1. For example, when the catalyst includespotassium (K⁺) and barium (Ba²⁺), the molar ratio between them (K:Ba),in one embodiment, is between about 1:4 and about 4:1. Also, when thecatalyst is prepared by mixing and heating K₂HPO₄, Ba(NO₃)₂, and H₃PO₄,the potassium and barium are present, in another embodiment, in a molarratio, K:Ba, between about 2:3 to about 1:1.

In one embodiment, the catalyst can include an inert support that isconstructed of a material comprising silicates, aluminates, carbons,metal oxides, and mixtures thereof. Alternatively, the carrier is inertrelative to the reaction mixture expected to contact the catalyst. Inanother embodiment, the method of preparing the catalyst can furtherinclude mixing an inert support with the catalyst before, during, orafter the mixing and heating of the phosphorus containing compounds,wherein the inert support includes silicates, aluminates, carbons, metaloxides, and mixtures thereof. In yet another embodiment, the method ofpreparing the catalyst can further include mixing an inert support withthe catalyst before, during, or after the mixing and heating of thephosphorus containing compounds and the non-phosphorus containingcompounds, wherein the inert support includes silicates, aluminates,carbons, metal oxides, and mixtures thereof.

Mixing of the phosphorus containing compounds or the phosphoruscontaining and non-phosphorus containing compounds of the catalyst canbe performed by any method known to those skilled in the art, such as,by way of example and not limitation: solid mixing and co-precipitation.In the solid mixing method, the various components are physically mixedtogether with optional grinding using any method known to those skilledin the art, such as, by way of example and not limitation, shear,extensional, kneading, extrusion, and others. In the co-precipitationmethod, an aqueous solution or suspension of the various components,including one or more of the phosphate compounds, is prepared, followedby optional filtration and heating to remove solvents and volatilematerials (e.g., water, nitric acid, carbon dioxide, ammonia, or aceticacid). The heating is typically done using any method known to thoseskilled in the art, such as, by way of example and not limitation,convection, conduction, radiation, microwave heating, and others.

In one embodiment of the invention, the catalyst is calcined.Calcination is a process that allows chemical reaction and/or thermaldecomposition and/or phase transition and/or removal of volatilematerials. The calcination process is carried out with any equipmentknown to those skilled in the art, such as, by way of example and notlimitation, furnaces or reactors of various designs, including shaftfurnaces, rotary kilns, hearth furnaces, and fluidized bed reactors. Thecalcination temperature is, in one embodiment, about 200° C. to about1200° C.; in another embodiment, the calcination temperature is about250° C. to about 900° C.; and in yet another embodiment, the calcinationtemperature is about 300° C. to 600° C. The calcination time is, in oneembodiment, about one hour to about seventy-two hours.

While many methods and machines are known to those skilled in the artfor fractionating particles into discreet sizes and determining particlesize distribution, sieving is one of the easiest, least expensive, andcommon ways. An alternative way to determine the size distribution ofparticles is with light scattering. Following calcination, the catalystis, in one embodiment, ground and sieved to provide a more uniformproduct. The particle size distribution of the catalyst particlesincludes a particle span that, in one embodiment, is less than about 3;in another embodiment, the particle size distribution of the catalystparticles includes a particle span that is less than about 2; and in yetanother embodiment, the particle size distribution of the catalystparticles includes a particle span that is less than about 1.5. Inanother embodiment of the invention, the catalyst is sieved to a medianparticle size of about 50 μm to about 500 μm. In another embodiment ofthe invention, the catalyst is sieved to a median particle size of about100 ρm to about 200 μm.

In another embodiment, the catalyst is prepared by the following steps,which comprise: (a) combining a phosphorus containing compound, anitrate salt, phosphoric acid, and water to give a wet mixture, whereinthe molar ratio between phosphorus and the cations is about 1, (b)calcining the wet mixture stepwise at about 50° C., about 80° C., about120° C., and about 450° C. to about 550° C. to give a dried solid, and(c) grinding and sieving the dried solid to about 100 μm to about 200μm, to produce the catalyst.

In another embodiment, the catalyst is prepared by the following steps,which comprise: (a) combining MnPO₄.qH₂O, KNO₃, and H₃PO₄, in a molarratio of about 0.3:1:1, on an anhydrous basis, and water to give a wetmixture, (b) calcining the wet mixture stepwise at about 50° C., about80° C., about 120° C., and about 450° C. to about 550° C. to give adried solid, and (c) grinding and sieving the dried solid to about 100μm to about 200 μm, to produce the catalyst.

In another embodiment, the catalyst is prepared by the following steps,which comprise: (a) combining Ca₂P₂O₇, KNO₃, and H₃PO₄, in a molar ratioof about 1.6:1:1, and water to give a wet mixture, (b) calcining the wetmixture stepwise at about 50° C., about 80° C., about 120° C., and about450° C. to about 550° C. to give a dried solid, and (c) grinding andsieving the dried solid to about 100 μm to about 200 μm, to produce thecatalyst.

In another embodiment, the catalyst is prepared by the following steps,which comprise: (a) combining a phosphorus containing compound, anitrate salt, phosphoric acid, and water to form a wet mixture, whereinthe molar ratio between phosphorus and the cations in both thephosphorus containing compound and nitrate salt is about 1, (b) heatingthe wet mixture to about 80° C. with stirring until near dryness toproduce a wet solid, (c) calcining the wet solid stepwise at about 50°C., about 80° C., about 120° C., and about 450° C. to about 550° C. togive a dried solid, and (d) grinding and sieving the dried solid toabout 100 μm to about 200 μm, to produce the catalyst.

In another embodiment, the catalyst is prepared by the following steps,which comprise: (a) combining Ba(NO₃)₂, K₂HPO₄, and H₃PO₄, in a molarratio of about 3:1:4, and water to give a wet mixture, (b) heating thewet mixture to about 80° C. with stirring until near dryness to form awet solid, (c) calcining the wet solid stepwise at about 50° C., about80° C., about 120° C., and about 450° C. to about 550° C. to give adried solid, and (d) grinding and sieving the dried solid to about 100μm to about 200 μm, to produce the catalyst.

In another embodiment, the catalyst is prepared by the following steps,which comprise: (a) combining Mn(NO₃)₂.4H₂O, K₂HPO₄, and H₃PO₄, in amolar ratio of about 1:1.5:2, and water to give a wet mixture, (b)heating the wet mixture to about 80° C. with stirring until near drynessto form a wet solid, (c) calcining the wet solid stepwise at about 50°C., about 80° C., about 120° C., and about 450° C. to about 550° C. togive a dried solid, and (d) grinding and sieving the dried solid toabout 100 μm to about 200 μm, to produce the catalyst.

In another embodiment, the catalyst is prepared by the following steps,which comprise: (a) combining Ca₂P₂O₇ and KH₂PO₄ in a molar ratio ofabout 3:1 to give a solid mixture, and (b) calcining the solid mixturestepwise at about 50° C., about 80° C., about 120° C., and about 450° C.to about 550° C., to produce the catalyst.

Following calcination and optional grinding and sieving, the catalystcan be utilized to catalyze several chemical reactions. Non-limitingexamples of reactions are: dehydration of hydroxypropionic acid toacrylic acid (as described in further detail below), dehydration ofglycerin to acrolein, dehydration of aliphatic alcohols to alkenes orolefins, dehydrogenation of aliphatic alcohols to ethers, otherdehydrogenations, hydrolyses, alkylations, dealkylations, oxidations,disproportionations, esterifications, cyclizations, isomerizations,condensations, aromatizations, polymerizations, and other reactions thatmay be apparent to those having ordinary skill in the art.

V Process for the Production of Acrylic Acid or its Derivatives fromHydroxypropionic Acid or its Derivatives

A process for converting hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof to acrylic acid, acrylic acidderivatives, or mixtures thereof of the present invention comprises thefollowing steps: a) providing an aqueous solution comprisinghydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof, wherein the hydroxypropionic acid is in monomeric form in theaqueous solution; b) combining the aqueous solution with an inert gas toform an aqueous solution/gas blend; c) evaporating the aqueous solutiongas/blend to produce a gaseous mixture; and d) dehydrating the gaseousmixture by contacting the mixture with a dehydration catalyst under apressure of at least about 80 psig.

Hydroxypropionic acid can be 3-hydroxypropionic acid, 2-hydroxypropionicacid (also called, lactic acid), 2-methyl hydroxypropionic acid, ormixtures thereof. Derivatives of hydroxypropionic acid can be metal orammonium salts of hydroxypropionic acid, alkyl esters ofhydroxypropionic acid, alkyl esters of 2-methyl hydroxypropionic acid,cyclic di-esters of hydroxypropionic acid, hydroxypropionic acidanhydride, or a mixture thereof. Non-limiting examples of metal salts ofhydroxypropionic acid are sodium hydroxypropionate, potassiumhydroxypropionate, and calcium hydroxypropionate. Non-limiting examplesof alkyl esters of hydroxypropionic acid are methyl hydroxypropionate,ethyl hydroxypropionate, butyl hydroxypropionate, 2-ethylhexylhydroxypropionate, or mixtures thereof. A non-limiting example of cyclicdi-esters of hydroxypropionic acid is dilactide.

Hydroxypropionic acid can be in monomeric form or as oligomers in anaqueous solution of hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof. In one embodiment, the oligomers ofthe hydroxypropionic acid in an aqueous solution of hydroxypropionicacid, hydroxypropionic acid derivatives, or mixtures thereof are lessthan about 25 wt % based on the total amount of hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof. In anotherembodiment, the oligomers of the hydroxypropionic acid in an aqueoussolution of hydroxypropionic acid, hydroxypropionic acid derivatives, ormixtures thereof are less than about 10 wt % based on the total amountof hydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof. In another embodiment, the oligomers of the hydroxypropionicacid in an aqueous solution of hydroxypropionic acid, hydroxypropionicacid derivatives, or mixtures thereof are less than about 5 wt % basedon the total amount of hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof. In yet another embodiment, thehydroxypropionic acid is in monomeric form in an aqueous solution ofhydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof. The process steps to remove the oligomers from the aqueoussolution can be purification or diluting with water and heating. In oneembodiment, the heating step can involve heating the aqueous solution ofhydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof at a temperature from about 50° C. to about 100° C. to removethe oligomers of the hydroxypropionic acid. In another embodiment, theheating step can involve heating the lactic acid aqueous solution at atemperature from about 95° C. to about 100° C. to remove the oligomersof the lactic acid and produce a monomeric lactic acid aqueous solutioncomprising at least 95 wt % of lactic acid in monomeric form based onthe total amount of lactic acid. In another embodiment, an about 88 wt %lactic acid aqueous solution (e.g. from Purac Corp., Lincolnshire, Ill.)is diluted with water to form an about 20 wt % lactic acid aqueoussolution, to remove the ester impurities that are produced from theintermolecular condensation reaction. These esters can result in loss ofproduct due to their high boiling point and oligomerization in theevaporation stage of the process. Additionally, these esters can causecoking, catalyst deactivation, and reactor plugging. As the watercontent decreases in the aqueous solution, the loss of feed material tothe catalytic reaction, due to losses in the evaporation step,increases.

In one embodiment, the hydroxypropionic acid is lactic acid or 2-methyllactic acid. In another embodiment, the hydroxypropionic acid is lacticacid. Lactic acid can be L-lactic acid, D-lactic acid, or mixturesthereof. In one embodiment, the hydroxypropionic acid derivative ismethyl lactate. Methyl lactate can be neat or in an aqueous solution.

Acrylic acid derivatives can be metal or ammonium salts of acrylic acid,alkyl esters of acrylic acid, acrylic acid oligomers, or a mixturethereof. Non-limiting examples of metal salts of acrylic acid are sodiumacrylate, potassium acrylate, and calcium acrylate. Non-limitingexamples of alkyl esters of acrylic acid are methyl acrylate, ethylacrylate, butyl acrylate, 2-ethylhexyl acrylate, or mixtures thereof.

In one embodiment, the concentration of the hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof in the aqueoussolution is between about 5 wt % and about 50 wt %. In anotherembodiment, the concentration of the hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof in the aqueoussolution is between about 10 wt % and about 25 wt %. In yet anotherembodiment, the concentration of the hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof in the aqueoussolution is about 20 wt %.

The aqueous solution can be combined with an inert gas to form anaqueous solution/gas blend. Non-limiting examples of the inert gas areair, nitrogen, helium, argon, carbon dioxide, carbon monoxide, steam,and mixtures thereof. The inert gas can be introduced to the evaporatingstep separately or in combination with the aqueous solution. The aqueoussolution can be introduced with a simple tube or through atomizationnozzles. Non-limiting examples of atomization nozzles include fannozzles, pressure swirl atomizers, air blast atomizers, two-fluidatomizers, rotary atomizers, and supercritical carbon dioxide atomizers.In one embodiment, the droplets of the aqueous solution are less thanabout 500 μm in diameter. In another embodiment, the droplets of theaqueous solution are less than about 200 μm in diameter. In yet anotherembodiment, the droplets of the aqueous solution are less than about 100μm in diameter.

In the evaporating step, the aqueous solution/gas blend is heated togive a gaseous mixture. In one embodiment, the temperature during theevaporating step is from about 165° C. to about 450° C. In anotherembodiment, the temperature during the evaporating step is from about250° C. to about 375° C. In one embodiment, the gas hourly spacevelocity (GHSV) in the evaporating step is from about 720 h⁻¹ to 3,600h⁻¹. In another embodiment, the gas hourly space velocity (GHSV) in theevaporating step is about 7,200 h⁻¹. The evaporating step can beperformed at either atmospheric pressure or higher pressure. In oneembodiment, the evaporating step is performed under a pressure fromabout 80 psig to about 550 psig. In another embodiment, the evaporatingstep is performed under a pressure from about 300 psig to about 400psig. In yet another embodiment, the evaporating step is performed undera pressure from about 350 psig to about 375 psig. In one embodiment, thegaseous mixture comprises from about 0.5 mol % to about 50 mol %hydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof. In another embodiment, the gaseous mixture comprises from about1 mol % to about 10 mol % hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof. In another embodiment, the gaseousmixture comprises from about 1.5 mol % to about 3.5 mol %hydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof. In another embodiment, the gaseous mixture comprises about 2.5mol % hydroxypropionic acid, hydroxypropionic acid derivatives, ormixtures thereof.

The evaporating step can be performed in various types of equipment,such as, but not limited to, plate heat exchanger, empty flow reactor,and fixed bed flow reactor. Regardless of the type of the reactor, inone embodiment, the reactor has an interior surface comprising materialselected from the group consisting of quartz, borosilicate glass,silicon, hastelloy, inconel, manufactured sapphire, stainless steel, andmixtures thereof. In another embodiment, the reactor has an interiorsurface comprising material selected from the group consisting ofquartz, borosilicate glass, and mixtures thereof. The evaporating stepcan be performed in a reactor with the aqueous solution flowing down, orflowing up, or flowing horizontally. In one embodiment, the evaporatingstep is performed in a reactor with the aqueous solution flowing down.Also, the evaporating step can be done in a batch form.

The gaseous mixture from the evaporating step is converted to acrylicacid, acrylic acid derivatives, and mixture thereof by contact it with adehydration catalyst in the dehydrating step. The dehydration catalystcan be selected from the group comprising sulfates, phosphates, metaloxides, aluminates, silicates, aluminosilicates (e.g., zeolites),arsenates, nitrates, vanadates, niobates, tantalates, selenates,arsenatophosphates, phosphoaluminates, phosphoborates, phosphocromates,phosphomolybdates, phosphosilicates, phosphosulfates, phosphotungstates,and mixtures thereof, and others that may be apparent to those havingordinary skill in the art. The catalyst can contain an inert supportthat is constructed of a material comprising silicates, aluminates,carbons, metal oxides, and mixtures thereof. In one embodiment, thedehydrating step is performed in a reactor, wherein the reactor has aninterior surface comprising material selected from the group consistingof quartz, borosilicate glass, silicon, hastelloy, inconel, manufacturedsapphire, stainless steel, and mixtures thereof. In another embodiment,the dehydrating step is performed in a reactor, wherein the reactor hasan interior surface comprising material selected from the groupconsisting of quartz, borosilicate glass, and mixtures thereof. In oneembodiment, the temperature during the dehydrating step is from about150° C. to about 500° C. In another embodiment, the temperature duringthe dehydrating step is from about 300° C. to about 450° C. In oneembodiment, the GHSV in the dehydrating step is from about 720 h⁻¹ toabout 36,000 h⁻¹. In another embodiment, the GHSV in the dehydratingstep is about 3,600 h⁻¹. The dehydrating step can be performed at higherthan atmospheric pressure. In one embodiment, the dehydrating step isperformed under a pressure of at least about 80 psig. In anotherembodiment, the dehydrating step is performed under a pressure fromabout 80 psig to about 550 psig. In another embodiment, the dehydratingstep is performed under a pressure from about 150 psig to about 500psig. In yet another embodiment, the dehydrating step is performed undera pressure from about 300 psig to about 400 psig. The dehydrating stepcan be performed in a reactor with the gaseous mixture flowing down,flowing up, or flowing horizontally. In one embodiment, the dehydratingstep is performed in a reactor with the gaseous mixture flowing down.Also, the dehydrating step can be done in a batch form.

In one embodiment, the evaporating and dehydrating steps are combined ina single step. In another embodiment, the evaporating and dehydratingsteps are performed sequentially in a single reactor. In yet anotherembodiment, the evaporating and dehydrating steps are performedsequentially in a tandem reactor.

In one embodiment, the selectivity of acrylic acid, acrylic acidderivatives, and mixture thereof from hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof is at least about50%. In another embodiment, the selectivity of acrylic acid, acrylicacid derivatives, and mixture thereof from hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof is at least about80%. In one embodiment, the selectivity of propanoic acid fromhydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof is less than about 5%. In another embodiment, the selectivity ofpropanoic acid from hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof is less than about 1%. In oneembodiment, the conversion of the hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof is more thanabout 50%. In another embodiment, the conversion of the hydroxypropionicacid, hydroxypropionic acid derivatives, or mixtures thereof is morethan about 80%.

In another embodiment of the present invention, a process for convertinghydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof to acrylic acid, acrylic acid derivatives, or mixtures thereofis provided. The process comprises the following steps: a) providing anaqueous solution comprising hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof, wherein the hydroxypropionic acidcomprises oligomers in the aqueous solution; b) heating the aqueoussolution at a temperature from about 50° C. to about 100° C. to removethe oligomers of the hydroxypropionic acid and produce an aqueoussolution of monomeric hydroxypropionic acid; c) combining the aqueoussolution of monomeric hydroxypropionic acid with an inert gas to form anaqueous solution/gas blend; d) evaporating the aqueous solutiongas/blend to produce a gaseous mixture; and e) dehydrating the gaseousmixture by contacting the mixture with a dehydration catalyst andproducing the acrylic acid, acrylic acid derivatives, or mixturesthereof.

In one embodiment, after the heating step, the concentration of theoligomers of the hydroxypropionic acid in the aqueous solution ofmonomeric of monomeric hydroxypropionic acid is less than about 20 wt %based on the total amount of hydroxypropionic acid, hydroxypropionicacid derivatives, or mixtures thereof. In another embodiment, after theheating step, the concentration of the oligomers of the hydroxypropionicacid in the aqueous solution of monomeric of monomeric hydroxypropionicacid is less than about 5 wt % based on the total amount ofhydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof.

In another embodiment of the present invention, a process for convertinghydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof to acrylic acid, acrylic acid derivatives, and mixture thereofis provided. The process comprises the following steps: a) providing anaqueous solution comprising hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof, wherein the hydroxypropionic acid isin monomeric form in the aqueous solution; b) combining the aqueoussolution with an inert gas to form an aqueous solution/gas blend; c)evaporating the aqueous solution/gas blend to produce a gaseous mixture;d) dehydrating the gaseous mixture by contacting the mixture with adehydration catalyst producing acrylic acid, and/or acrylates; and e)cooling the acrylic acid, acrylic acid derivatives, and mixture thereofat a GHSV of more than about 360 h⁻¹.

The stream of acrylic acid, acrylic acid derivatives, and mixturethereof produced in the dehydrating step is cooled to give an aqueousacrylic acid composition as the product stream. The time required tocool stream of the acrylic acid, acrylic acid derivatives, or mixturesthereof must be controlled to reduce the decomposition of acrylic acidto ethylene and polymerization. In one embodiment, the GHSV of theacrylic acid, acrylic acid derivatives, and mixture thereof in thecooling step is more than about 720 h⁻¹.

In another embodiment of the present invention, a process for convertinglactic acid to acrylic acid is provided. The process comprises thefollowing steps: a) diluting an about 88 wt % lactic acid aqueoussolution with water to form an about 20 wt % lactic acid aqueoussolution; b) heating the about 20 wt % lactic acid aqueous solution at atemperature of about 95° C. to about 100° C. to remove oligomers of thelactic acid, producing a monomeric lactic acid solution comprising atleast about 95 wt % of the lactic acid in monomeric form based on thetotal amount of lactic acid; c) combining the monomeric lactic acidsolution with nitrogen to form an aqueous solution/gas blend; d)evaporating the aqueous solution/gas blend in a reactor with insidesurface of borosilicate glass at a GHSV of about 7,200 h⁻¹ at atemperature from about 300° C. to about 350° C. to produce a gaseousmixture comprising about 2.5 mol % lactic acid and about 50 mol % water;e) dehydrating the gaseous mixture in a reactor with inside surface ofborosilicate glass at a GHSV of about 3,600 h⁻¹ at a temperature of 350°C. to about 425° C. by contacting the mixture with a dehydrationcatalyst under a pressure of about 360 psig, producing the acrylic acid;and f) cooling the acrylic acid at a GHSV from about 360 h⁻¹ to about36,000 h⁻¹.

In another embodiment of the present invention, a process for convertinghydroxypropionic acid, derivatives of hydroxypropionic acid, andmixtures thereof to acrylic acid, acrylic acid derivatives, or mixturesthereof is provided. The process comprises the following steps: a)providing an aqueous solution comprising hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof, wherein thehydroxypropionic acid is in monomeric form in the aqueous solution, andwherein the hydroxypropionic acid, hydroxypropionic acid derivatives, ormixtures thereof comprise from about 10 wt % to about 25 wt % of theaqueous solution; b) combining the aqueous solution with an inert gas toform an aqueous solution/gas blend; c) evaporating the aqueoussolution/gas blend to produce a gaseous mixture; and d) dehydrating thegaseous mixture by contacting the mixture with a dehydration catalystproducing acrylic acid, acrylic acid derivatives, or mixtures thereof.

In another embodiment of the present invention, a process for convertingalkyl lactates to acrylic acid, acrylic acid derivatives, or mixturesthereof is provided. The process comprises the following steps: a)providing alkyl lactates or a solution comprising alkyl lactates and asolvent; b) combining the alkyl lactates or the solution comprising thealkyl lactates and the solvent with an inert gas to form a liquid/gasblend; c) evaporating the liquid/gas blend to produce a gaseous mixture;and d) dehydrating the gaseous mixture by contacting the gaseous mixturewith a dehydration catalyst under a pressure of at least about 80 psig,producing acrylic acid, acrylic acid derivatives, or mixtures thereof.

In one embodiment, alkyl lactates are selected from the group consistingof methyl lactate, ethyl lactate, butyl lactate, 2-ethylhexyl lactate,and mixtures thereof. In another embodiment, the solvent is selectedfrom the group consisting of water, methanol, ethanol, butanol,2-ethylhexanol, isobutanol, isooctyl alcohol, and mixtures thereof.

In another embodiment, a process for converting hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof to acrylic acid,acrylic acid derivatives, or mixtures thereof is provided comprising thefollowing steps: a) providing a solution comprising hydroxypropionicacid, hydroxypropionic acid derivatives, or mixtures thereof; b)combining the solution with a gas to form a solution/gas blend; and c)dehydrating the solution/gas blend by contacting the solution/gas blendwith a dehydration catalyst.

VI Purification of Bio-Based Acrylic Acid to Crude and Glacial AcrylicAcid

In one embodiment, a glacial acrylic acid composition is providedcomprising at least about 98 wt % acrylic acid, and wherein a portion ofthe remaining impurities in the glacial acrylic acid composition ishydroxypropionic acid, hydroxypropionic acid derivatives, or mixturesthereof.

In one embodiment, a crude acrylic acid composition is providedcomprising between about 94 wt % and about 98 wt % acrylic acid, andwherein a portion of the remaining impurities in the glacial acrylicacid composition is hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof.

Hydroxypropionic acid can be 3-hydroxypropionic acid, 2-hydroxypropionicacid (also called, lactic acid), 2-methyl hydroxypropionic acid, ormixtures thereof. Derivatives of hydroxypropionic acid can be metal orammonium salts of hydroxypropionic acid, alkyl esters ofhydroxypropionic acid, alkyl esters of 2-methyl hydroxypropionic acid,cyclic di-esters of hydroxypropionic acid, hydroxypropionic acidanhydride, or a mixture thereof. Non-limiting examples of metal salts ofhydroxypropionic acid are sodium hydroxypropionate, potassiumhydroxypropionate, and calcium hydroxypropionate. Non-limiting examplesof alkyl esters of hydroxypropionic acid are methyl hydroxypropionate,ethyl hydroxypropionate, butyl hydroxypropionate, 2-ethylhexylhydroxypropionate, or mixtures thereof. A non-limiting example of cyclicdi-esters of hydroxypropionic acid is dilactide.

In one embodiment, the hydroxypropionic acid is lactic acid or 2-methyllactic acid. In another embodiment, the hydroxypropionic acid is lacticacid. Lactic acid can be L-lactic acid, D-lactic acid, or mixturesthereof. In one embodiment, the hydroxypropionic acid, hydroxypropionicacid derivatives, or mixtures thereof in the impurities in the glacialacrylic acid composition are lactic acid, lactic acid derivatives, ormixtures thereof. In another embodiment, the hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof in the impuritiesin the crude acrylic acid composition are lactic acid, lactic acidderivatives, or mixtures thereof.

In one embodiment, the concentration of the hydroxypropionic acid,hydroxypropionic acid derivatives, or mixtures thereof in the remainingimpurities of the glacial acrylic acid composition is less than about 2wt %, based on the total amount of the glacial acrylic acid composition.In another embodiment, the hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof in the remaining impurities of theglacial acrylic acid composition is less than about 1 wt %, based on thetotal amount of the glacial acrylic acid composition. In anotherembodiment, the hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof in the remaining impurities of theglacial acrylic acid composition is less than about 400 ppm, based onthe total amount of the glacial acrylic acid composition.

In one embodiment, the bio-based content of the glacial acrylic acid isgreater than about 3%. In another embodiment, the bio-based content ofthe glacial acrylic acid is greater than 30%. In yet another embodiment,the bio-based content of the glacial acrylic acid is greater than about90%. In one embodiment, the bio-based content of the crude acrylic acidis greater than about 3%. In another embodiment, the bio-based contentof the crude acrylic acid is greater than 30%. In yet anotherembodiment, the bio-based content of the crude acrylic acid is greaterthan about 90%.

The glacial or crude acrylic acid composition can be made from anaqueous solution of acrylic acid produced from renewable resources ormaterials and fed into the purification process to produce crude acrylicacid or glacial acrylic acid. Non-limiting examples of renewableresources or materials for the production of the aqueous solution ofacrylic acid are hydroxypropionic acid, hydroxypropionic acidderivatives, or mixtures thereof; glycerin; carbon monoxide and ethyleneoxide; carbon dioxide and ethylene; and crotonic acid. In oneembodiment, the renewable resources or materials are hydroxypropionicacid, hydroxypropionic acid derivatives, or mixtures thereof. In anotherembodiment, the renewable resources or materials are lactic acid, lacticacid derivatives, or mixtures thereof. In yet another embodiment, therenewable resource or material is lactic acid.

In one embodiment, the aqueous solution of acrylic acid comprises: 1)acrylic acid; 2) lactic acid, lactic acid derivatives, or mixturesthereof, and is essentially free of maleic anhydride, furfural, andformic acid. In another embodiment, the aqueous solution of acrylic acidhas from about 4 wt % to about 80 wt % acrylic acid. In anotherembodiment, the aqueous solution of acrylic acid has from about 4 wt %to about 40 wt % acrylic acid. In yet another embodiment, the aqueoussolution of acrylic acid has from about 5 wt % to about 25 wt % acrylicacid. In another embodiment, the aqueous solution of acrylic acid hasfrom about 8 wt % to about 16 wt % acrylic acid.

In one embodiment, the aqueous solution of acrylic acid has from about0.001 wt % to about 50 wt % lactic acid, lactic acid derivatives, ormixtures thereof. In another embodiment, the aqueous solution of acrylicacid has from about 0.001 wt % to about 20 wt % % lactic acid, lacticacid derivatives, or mixtures thereof. In yet another embodiment, theaqueous solution of acrylic acid has about 6 wt % % lactic acid, lacticacid derivatives, or mixtures thereof.

In one embodiment, the aqueous solution of acrylic acid has from about 8wt % to about 16 Wt % acrylic acid and from about 0.1 wt % to about 10wt % lactic acid, lactic acid derivatives, or mixtures thereof, andwherein the aqueous solution of acrylic acid is essentially free ofmaleic anhydride, furfural, and formic acid. Non-limiting examples ofimpurities that can be present in the aqueous solution of acrylic acidare acetaldehyde, acetic acid, and propanoic acid.

The aqueous solution of acrylic acid can be extracted with a solvent toproduce an extract. In one embodiment, the solvent is selected from thegroup consisting of ethyl acetate, isobutyl acetate, methyl acetate,toluene, dimethyl phthalate, hexane, pentane, diphenyl ether, ethylhexanoic acid, N-methylpyrrolidone, C6 to C10 paraffin fractions, andmixtures thereof. In another embodiment, the extraction solvent is ethylacetate. In one embodiment, the extraction solvent can form an azeotropewith water.

In one embodiment, the solvent comprises at least one polymerizationinhibitor. Non-limiting examples of polymerization inhibitors arephenothiazine and 4-methoxy phenol. In another embodiment, the glacialacrylic acid comprises from about 200 ppm to about 400 ppm4-methoxyphenol. In another embodiment, the polymerization inhibitor isadded to the aqueous solution of acrylic acid before the extractingstep.

After the extraction, the extract can be dried to produce a driedextract. The drying can be achieved with a variety of methods, such as,and not by way of limitation, distillation and sorption. In oneembodiment, the drying is performed by azeotropic distillation. Inanother embodiment, the sorption is performed on a solid powder. In yetanother embodiment, the solid powder is selected from the groupconsisting of magnesium sulfate, sodium sulfate, calcium sulfate,molecular sieves, metal hydrides, reactive metals, and mixtures thereof.In yet another embodiment, the sorption is performed with sodium sulfateand is followed by filtration to produce a dried filtrate.

The dried extract or dried filtrate can be further processed bydistillation to produce a distilled acrylic acid composition. In oneembodiment, the distillation is vacuum distillation at about 70 mm Hgand about 40° C. to produce a distilled crude acrylic acid composition,and is followed by a fractional distillation at about 40 mm Hg andcollecting fractions from 59° C. to 62° C. to produce the distilledacrylic acid composition.

In one embodiment, cooling of the distilled acrylic acid composition toa temperature from about −21° C. to about 14° C. produces crystals ofacrylic acid; partially melting the crystals of acrylic acid produces aliquid/solid mixture; decanting the liquid/solid mixture produces apurified acrylic acid solid composition; fully melting the purifiedacrylic acid solid composition produces a purified acrylic acid liquidcomposition; and determining acrylic acid purity of the purified acrylicacid liquid composition, and if the purity is less than about 98 wt %acrylic acid, repeating the cooling, partially melting, decanting, andfully melting steps on the purified acrylic acid liquid compositionuntil a purity of about 98 wt % acrylic acid is achieved and a glacialacrylic acid composition is produced.

In another embodiment, cooling of the distilled acrylic acid compositionto a temperature from about −21° C. to about 14° C. produces crystals ofacrylic acid; partially melting the crystals of acrylic acid produces aliquid/solid mixture; decanting the liquid/solid mixture produces apurified acrylic acid solid composition; fully melting the purifiedacrylic acid solid composition produces a purified acrylic acid liquidcomposition; and determining acrylic acid purity of the purified acrylicacid liquid composition, and if the purity is less than about 94 wt %acrylic acid, repeating the cooling, partially melting, decanting, andfully melting steps on the purified acrylic acid liquid compositionuntil a purity of about 94 wt % acrylic acid is achieved and a crudeacrylic acid composition is produced.

In yet another embodiment, cooling of the distilled acrylic acidcomposition to a temperature from about −21° C. to about 14° C. producescrystals of acrylic acid; partially melting the crystals of acrylic acidproduces a liquid/solid mixture; decanting the liquid/solid mixtureproduces a purified acrylic acid solid composition; fully melting thepurified acrylic acid solid composition produces a purified acrylic acidliquid composition; and determining acrylic acid purity of the purifiedacrylic acid liquid composition, and if the purity is less than about 99wt % acrylic acid, repeating the cooling, partially melting, decanting,and fully melting steps on the purified acrylic acid liquid compositionuntil a purity of about 99 wt % acrylic acid is achieved and a glacialacrylic acid composition is produced.

In one embodiment, the distilling step is followed by determining theacrylic acid purity of the distilled acrylic acid composition, and ifthe purity is less than about 98 wt % acrylic acid, repeating thedistilling step on the purified acrylic acid composition until a purityof about 98 wt % acrylic acid is achieved and a glacial acrylic acidcomposition is produced. In another embodiment, the distilling step isfollowed by determining the acrylic acid purity of the distilled acrylicacid composition, and if the purity is less than about 94 wt % acrylicacid, repeating the distilling step on the purified acrylic acidcomposition until a purity of about 94 wt % acrylic acid is achieved anda crude acrylic acid composition is produced.

In one embodiment, the distilled acrylic acid composition is cooled to atemperature from about 0° C. to about 5° C. to produce crystals ofacrylic acid.

In one embodiment of the present invention, the glacial acrylic acidcomposition is produced by the steps comprising: a) providing an aqueoussolution of acrylic acid comprising 1) acrylic acid and 2) lactic acid,lactic acid derivatives, or mixtures thereof, and wherein the aqueoussolution of acrylic acid is essentially free of maleic anhydride,furfural, and formic acid; b) extracting the aqueous solution of acrylicacid with a solvent to produce an extract; c) drying the extract toproduce a dried extract; d) distilling the dried extract to producecrude acrylic acid; e) cooling the crude acrylic acid to a temperaturefrom about −21° C. to about 14° C. to produce crystals of acrylic acid;f) partially melting the crystals of acrylic acid to produce aliquid/solid mixture; g) decanting the liquid/solid mixture to produce aacrylic acid solid composition; h) fully melting the purified acrylicacid solid composition to produce a purified acrylic acid composition;and i) determining the acrylic acid purity of the purified acrylic acidliquid composition and if the purity is less than 98 wt % acrylic acidrepeating the cooling, partially melting, decanting, and fully meltingsteps on the purified acrylic acid liquid composition until a purity ofabout 98 wt % is achieved to produce glacial acrylic acid composition.

In another embodiment of the present invention, a glacial acrylic acidcomposition is provided produced by the steps comprising: a) providingan aqueous solution of acrylic acid comprising: 1) acrylic acid; and 2)lactic acid, lactic acid derivatives, or mixtures thereof, and whereinthe aqueous solution of acrylic acid is essentially free of maleicanhydride, furfural, and formic acid; b) extracting the aqueous solutionof acrylic acid with a solvent to produce an extract; c) drying theextract to produce a dried extract; d) distilling the dried extract toproduce a distilled acrylic acid composition; and e) determining theacrylic acid purity of the distilled acrylic acid composition, and ifthe purity is less than about 98 wt % acrylic acid, repeating thedistilling step on the purified acrylic acid composition until a purityof about 98 wt % acrylic acid is achieved and the glacial acrylic acidcomposition is produced.

In one embodiment of the present invention, a crude acrylic acidcomposition is provided produced by the steps comprising: a) providingan aqueous solution of acrylic acid comprising: 1) acrylic acid; and 2)lactic acid, lactic acid derivatives, or mixtures thereof, and whereinthe aqueous solution of acrylic acid is essentially free of maleicanhydride, furfural, and formic acid; b) extracting the aqueous solutionof acrylic acid with a solvent to produce an extract; c) drying theextract to produce a dried extract; d) distilling the dried extract toproduce a distilled acrylic acid composition; and e) determining theacrylic acid purity of the distilled acrylic acid composition, and ifthe purity is less than about 94 wt % acrylic acid, repeating thedistilling step on the purified acrylic acid composition until a purityof about 94 wt % acrylic acid is achieved and the crude acrylic acidcomposition is produced.

In another embodiment of the present invention, a crude acrylic acidcomposition is provided produced by the steps comprising: a) providingan aqueous solution of acrylic acid comprising: 1) acrylic acid; and 2)lactic acid, lactic acid derivatives, or mixtures thereof, and whereinthe aqueous solution of acrylic acid is essentially free of maleicanhydride, furfural, and formic acid; b) extracting the aqueous solutionof acrylic acid with a solvent to produce an extract; c) drying theextract to produce a dried extract; d) distilling the dried extract toproduce a distilled acrylic acid composition; e) cooling the distilledacrylic acid composition to a temperature from about −21° C. to about14° C. to produce crystals of acrylic acid; f) partially melting thecrystals of acrylic acid to produce a liquid/solid mixture; g) decantingthe liquid/solid mixture to produce a purified acrylic acid solidcomposition; h) fully melting the purified acrylic acid solidcomposition to produce a purified acrylic acid liquid composition; andi) determining the acrylic acid purity of the purified acrylic acidliquid composition, and if the purity is less than about 94 wt % acrylicacid, repeating the cooling, partially melting, decanting, and fullymelting steps on the purified acrylic acid liquid composition until apurity of about 94 wt % acrylic acid is achieved and the crude acrylicacid composition is produced.

In one embodiment of the present invention, a glacial acrylic acidcomposition is provided comprising about 99 wt % acrylic acid, producedby the steps comprising: a) providing an aqueous solution of acrylicacid comprising: 1) from about 8 wt % to about 16 wt % acrylic acid; and2) from about 0.1 wt % to about 10 wt % lactic acid, lactic acidderivatives, or mixtures thereof, and wherein the aqueous solution ofacrylic acid is essentially free of maleic anhydride, furfural, andformic acid; b) extracting the aqueous solution of acrylic acid, withethyl acetate to produce an extract; c) drying the extract with sodiumsulfate to produce a dried extract; d) vacuum distilling the driedextract at about 70 mm Hg and 40° C. to produce a distilled crudeacrylic acid composition; e) fractionally distilling the distilled crudeacrylic acid composition at about 40 mm Hg and collecting fractions from59° C. to 62° C. to produce a distilled acrylic acid composition; f)cooling the distilled acrylic acid composition to a temperature fromabout 0° C. to about 5° C. to produce crystals of acrylic acid; g)partially melting the crystals of acrylic acid to produce a liquid/solidmixture; h) decanting the liquid/solid mixture to produce a purifiedacrylic acid solid composition; i) fully melting the purified acrylicacid composition to produce a purified acrylic acid liquid composition;and j) determining the acrylic acid purity of the purified acrylic acidliquid composition, and if the purity is less than about 99 wt % acrylicacid, repeating the cooling, partially melting, decanting, and fullymelting steps on the purified acrylic acid liquid composition until apurity of about 99 wt % acrylic acid is achieved and the glacial acrylicacid composition is produced.

VII Examples

The following examples are provided to illustrate the invention, but arenot intended to limit the scope thereof.

Example 1

Solid dibasic potassium phosphate, K₂HPO₄ (36.40 g, 209 mmol, ≧98%;Sigma—Aldrich Co., St. Louis, Mo.; catalog # P3786) was mixed quicklywith an aqueous solution of barium nitrate, Ba(NO₃)₂ (2050 mL of a 0.08g/mL stock solution, 627 mmol, 99.999%; Sigma—Aldrich Co., St. Louis,Mo.; catalog #202754) at room temperature. Phosphoric acid, H₃PO₄ (58.7mL of an 85 wt %, density=1.684 g/mL, 857 mmol; Acros Organics, Geel,Belgium; catalog #295700010), was added to the slurry, providing asolution containing potassium (K⁺, M^(I)) and Barium (Ba²⁺, M^(II))cations. The final pH of the suspension was about 1.6. Theacid-containing suspension was then dried slowly in a glass beaker at80° C. using a heating plate while magnetically stirring the suspensionuntil the liquid was evaporated and the material was almost completelydried. Heating was continued in a oven with air circulation (G1530A,HP6890 GC; Agilent Corp., Santa Clara, Calif.) at 50° C. for 5.3 h, thenat 80° C. for 10 h (0.5° C./min ramp), following by cooling down at 25°C. The material was calcined at 120° C. for 2 hours (0.5° C./min ramp)followed by 450° C. for 4 hours (2° C./min ramp) using the same oven.After calcination, the material was left inside the oven until it cooleddown by itself at a temperature below 25° C. before it was taken out ofthe oven. Finally, the catalyst was ground and sieved to about 100 μm toabout 200 μm.

Example 2

454 g of an 88 wt % L-lactic acid solution (Purac Corp., Lincolnshire,Ill.) was diluted with 1,300 g of water. The diluted solution was heatedto 95° C. and held at that temperature with stirring for about 4 to 12hours. Then, the solution was cooled to room temperature, and its lacticacid and lactic acid oligomers concentrations were measured by HPLC(Agilent 1100 system; Santa Clara, Calif.) equipped with a DAD detectorand a Waters Atlantis T3 column (Catalog #186003748; Milford, Mass.)using methods generally known by those having ordinary skill in the art.The solution was essentially free of oligomers. Finally, the solutionwas further diluted with water to yield a 20 wt % L-lactic acid aqueoussolution and essentially free of oligomers.

Example 3

The reactor consisted of an electric clam shell furnace (Applied Testsystems, Butler, Pa.) with an 8″ (20.3 cm) heated zone with onetemperature controller connected in series to another electric clamshell furnace (Applied Test Systems, Butler, Pa.) with a 16″ (40.6 cm)heated zone containing two temperature controllers and a reactor tube.The reactor tube consisted of a 13″ (33 cm) borosilicate glass-linedtube (SGE Analytical Science Pty Ltd., Ringwood, Australia)) and a 23″(58.4 cm) borosilicate glass lined tube connected in series using aSwagelok™ tee fitting equipped with an internal thermocouple and havingan inside diameter of 9.5 mm. The head of the column was fitted with a⅛″ (3.2 mm) stainless steel nitrogen feed line and a 1/16″ (1.6 mm)fused silica lined stainless steel liquid feed supply line connected toa HPLC pump (Smartline 100, Knauer, Berlin, Germany) that was connectedto a lactic acid feed tank. The bottom of the reactor was connected to aTeflon-lined catch tank using ⅛″ (3.2 mm) fused silica lined stainlesssteel tubing and Swagelok∩ fittings. The reactor column was packed witha plug of glass wool, 13 g of fused quartz, 16″ (40.7 cm) with catalystof Example 1 (47 g and 28.8 mL packed bed volume) and topped with 25 gof fused quartz. The reactor tube was placed in an aluminum block andplaced into the reactor from above in a downward flow. The reactor waspreheated to 375° C. overnight under 0.25 L/min nitrogen. The nitrogenfeed was increased to 0.85 L/min during the experiment. The liquid feedwas a 20 wt % aqueous solution of L-lactic acid, prepared as in Example2, and fed at 0.845 mL/min (LHSV of 1.8 h⁻; 50.7 g/h), giving aresidence time of about 1 s (GHSV of 3,600 h⁻¹) at STP conditions. Theclam shell heaters were adjusted to give an internal temperature about350° C. After flowing through the reactor, the gaseous stream was cooledand the liquid was collected in the catch tank for analysis by off-lineHPLC using an Agilent 1100 system (Santa Clara, Calif.) equipped with aDAD detector and a Waters Atlantis T3 column (Catalog #186003748;Milford, Mass.) using methods generally known by those having ordinaryskill in the art. The gaseous stream was analyzed on-line by GC using anAgilent 7890 system (Santa Clara, Calif.) equipped with a FID detectorand Varian CP-Para Bond Q column (Catalog # CP7351; Santa Clara,Calif.). The crude reaction mixture was cooled and collected over 159 hto give 748 g acrylic acid as a crude mixture in 54% yield, 75% acrylicacid selectivity, and 69% conversion of lactic acid. The acrylic acidyield, corrected for the losses during the evaporating step, was 61% andits selectivity was 89%. The acrylic acid aqueous concentration was 8.4wt %, and that of lactic acid was 6.3 wt %.

Example 4

The reaction mixtures from Example 3 were combined into four batches andisolated to give an acrylic acid solution of 668.9 g of acrylic acid inwater. A stabilizer (200-400 ppm phenothiazine) was added to each batchand the batches were extracted with ethyl acetate several times. Thecombined ethyl acetate layers were dried with sodium sulfate, treatedwith activated carbon, filtered over diatomaceous earth, and washed withethyl acetate. The filtrate was evaporated at 40-70 mm Hg with a bathtemperature of 23° C.-40° C. to give bio-based acrylic acid as a paleyellow liquid (81.4% yield). The bio-based acrylic acid was thenfractionally distilled using a 12 inch 14/20 Vigreux column. The productwas collected with head temperature of 59-62° C., stabilized with4-methoxy phenol, and placed in a 3-5° C. fridge overnight. The solutionwas removed from the fridge and thawed slightly. The resulting liquidwas decanted off and the solids were combined. The crystallization wasrepeated several times. The four batches were combined to give glacialacrylic acid (218 g, 32.6% yield on purification). The glacial acrylicacid composition consisted of 99.1 wt % acrylic acid, 0.1 wt % water,0.7 wt % propanoic acid, and 0.1 wt % lactic acid.

Example 5

The cross-linker methylene bis-acrylamide (MBAA; 0.963 g, 0.006 mol) wasdissolved in bio-based acrylic acid from Example 4 (150 g, 2.08 mol) bystirring in a holding beaker. The solution was then added dropwise via apipette while stirring to 124.9 g of 50 wt % solution of NaOH (1.56 mol)in a 1 L reactor equipped with magnetic stirrer. The reactor was placedin an ice bath to remove the heat released by the neutralization. Asmall amount of water (10 g) was used to rinse the pipette and originalbio-based acrylic acid/MBAA holding beaker. Once the temperature of theneutralized acrylic acid became about 20° C., the reactor was removedfrom the ice bath. Water was added to the reaction mixture to make thewhole weight of the mixture equal to 474 g. The reactor was then closedand insulated (Baysilone paste for insulation of the glass surfaces ofvessel and lid, in addition to Teflon tape on the outside where the lidmet the vessel). The reaction mixture was purged with argon for at least20 min. The reactor was equipped with a syringe needle to allow forpressure equilibration. The reactor was then placed on a stir plate.0.15 g of the initiator V50(2,2′-azobis(2-methylpropionamidine)dihydrochloride; Wako Pure

Chemical Industries, Ltd; Osaka, Japan) was injected in the mixturewhile stirring and was allowed to homogenize for another 10 min. Two UVlamps equipped with side mirrors were placed on both sides of thereactor in a way to surround it as much as possible. When the light wasturned on, the temperature vs. time started being recorded. The reactiontemperature started increasing after certain time and reached typically40° C. to 70° C., after which it starts slowly decreasing. The gellationwas observed by the decreasing rotation speed of the stir bar, whichthen came to a complete stop. After the temperature started droppingsteadily below the maximum point (about 30 min after the temperaturestarted increasing above room temperature), the reactor was removed andplaced in a circulation oven preset at 60° C. and stayed there overnight(at least 18 hours). On the next day, the reactor was removed from theoven and allowed to cool for one hour. The gel was carefully removedfrom the reactor and wet-ground through a steel mesh onto severalTeflon-ized metal trays that were then placed in an oven at 80° C. and10 mbar vacuum over 3 days. The dried superabsorbent polymer was thenmilled in a regular commercial mill (Retsch GmbH; Haan, Germany) andsieved through a set of meshes to obtain the 150 μm-850 μm particle sizedistribution cut. The so obtained superabsorbent polymer powder wastested for cylinder retention capacity (CRC), extractables, andabsorption against pressure (AAP). The results were the same as thoseobtained from the testing of petroleum-based superabsorbent polymer,prepared under the same conditions as the bio-based superabsorbentpolymer, to within experimental error.

Example 6

The superabsorbent polymer powder of Example 5 was tested for cylinderretention capacity (CRC), extractables, and absorption against pressure(AAP) using the methods described the “Test and Calculation Procedures”section below. The results are shown in Table 1 below, along withresults from the same tests on petroleum-based SAP prepared under thesame conditions as in Example 5.

TABLE 1 SAP Property Bio- Petroleum- based SAP based SAP Cylinderretention capacity (CRC), [g/g] 43.3 40.2 Extractables, [%] 7.3 7.7Absorption against pressure (AAP), [g/g] 34.4 33.1

The results showed that bio-based SAP and petroleum-based SAP had thesame properties, to within experimental error.

Example 7

The bio-based content of the superabsorbent polymer composition ofExample 4 is measured in accordance with ASTM D6866 Method B, asdescribed in the Test and Calculation Procedures section below, and isgreater than about 90%.

VIII Test and Calculation Procedures

Extractables: the extractable fractions of the water-absorbingsuperabsorbent polymer particles are measured in accordance with INDAtest method WSP 270.2, incorporated herein by reference.

Cylinder retention capacity (CRC): it is measured in accordance withINDA test method WSP 241.2, incorporated herein by reference.

Absorption against pressure (AAP): it is measured in accordance withINDA test method WSP 242.2, incorporated herein by reference.

Residual monomer: it is measured in accordance with INDA test method WSP210.2, incorporated herein by reference.

The above tests and measurements should be carried out, unless otherwisestated, at an ambient temperature of 23±2° C. and relative humidity of50±10%.

Bio-based content: the bio-based content of a material is measured usingthe ASTM D6866 method, which allows the determination of the bio-basedcontent of materials using radiocarbon analysis by accelerator massspectrometry, liquid scintillation counting, and isotope massspectrometry. When nitrogen in the atmosphere is struck by anultraviolet light produced neutron, it loses a proton and forms carbonthat has a molecular weight of 14, which is radioactive. This ¹⁴C isimmediately oxidized into carbon dioxide, which represents a small, butmeasurable fraction of atmospheric carbon. Atmospheric carbon dioxide iscycled by green plants to make organic molecules during the processknown as photosynthesis. The cycle is completed when the green plants orother forms of life metabolize the organic molecules producing carbondioxide, which causes the release of carbon dioxide back to theatmosphere. Virtually all forms of life on Earth depend on this greenplant production of organic molecules to produce the chemical energythat facilitates growth and reproduction. Therefore, the ¹⁴C that existsin the atmosphere becomes part of all life forms and their biologicalproducts. These renewably based organic molecules that biodegrade tocarbon dioxide do not contribute to global warming because no netincrease of carbon is emitted to the atmosphere. In contrast, fossilfuel-based carbon does not have the signature radiocarbon ratio ofatmospheric carbon dioxide. See WO 2009/155086, incorporated herein byreference.

The application of ASTM D6866 to derive a “bio-based content” is builton the same concepts as radiocarbon dating, but without use of the ageequations. The analysis is performed by deriving a ratio of the amountof radiocarbon (¹⁴C) in an unknown sample to that of a modern referencestandard. The ratio is reported as a percentage with the units “pMC”(percent modern carbon). If the material being analyzed is a mixture ofpresent day radiocarbon and fossil carbon (containing no radiocarbon),then the pMC value obtained correlates directly to the amount of biomassmaterial present in the sample. The modern reference standard used inradiocarbon dating is a NIST (National Institute of Standards andTechnology) standard with a known radiocarbon content equivalentapproximately to the year AD 1950. The year AD 1950 was chosen becauseit represented a time prior to thermo-nuclear weapons testing, whichintroduced large amounts of excess radiocarbon into the atmosphere witheach explosion (termed “bomb carbon”). The AD 1950 reference represents100 pMC. “Bomb carbon” in the atmosphere reached almost twice normallevels in 1963 at the peak of testing and prior to the treaty haltingthe testing. Its distribution within the atmosphere has beenapproximated since its appearance, showing values that are greater than100 pMC for plants and animals living since AD 1950. The distribution ofbomb carbon has gradually decreased over time, with today's value beingnear 107.5 pMC. As a result, a fresh biomass material, such as corn,could result in a radiocarbon signature near 107.5 pMC.

Petroleum-based carbon does not have the signature radiocarbon ratio ofatmospheric carbon dioxide. Research has noted that fossil fuels andpetrochemicals have less than about 1 pMC, and typically less than about0.1 pMC, for example, less than about 0.03 pMC. However, compoundsderived entirely from renewable resources have at least about 95 percentmodern carbon (pMC), they may have at least about 99 pMC, includingabout 100 pMC.

Combining fossil carbon with present day carbon into a material willresult in a dilution of the present day pMC content. By presuming that107.5 pMC represents present day biomass materials and 0 pMC representspetroleum derivatives, the measured pMC value for that material willreflect the proportions of the two component types. A material derived100% from present day soybeans would give a radiocarbon signature near107.5 pMC. If that material was diluted with 50% petroleum derivatives,it would give a radiocarbon signature near 54 pMC.

A bio-based content result is derived by assigning 100% equal to 107.5pMC and 0% equal to 0 pMC. In this regard, a sample measuring 99 pMCwill give an equivalent bio-based content result of 93%.

Assessment of the materials described herein was done in accordance withASTM D6866, particularly with Method B. The mean values encompass anabsolute range of 6% (plus and minus 3% on either side of the bio-basedcontent value) to account for variations in end-component radiocarbonsignatures. It is presumed that all materials are present day or fossilin origin and that the desired result is the amount of bio-component“present” in the material, not the amount of bio-material “used” in themanufacturing process.

Other techniques for assessing the bio-based content of materials aredescribed in U.S. Pat. Nos. 3,885,155, 4,427,884, 4,973,841, 5,438,194,and 5,661,299, and WO 2009/155086, each incorporated herein byreference.

For example, acrylic acid contains three carbon atoms in its structuralunit. If acrylic acid is derived from a renewable resource, then ittheoretically has a bio-based content of 100%, because all of the carbonatoms are derived from a renewable resource.

The foregoing description is given for clearness of understanding only,and no unnecessary limitations should be understood therefrom, asmodifications within the scope of the invention may be apparent to thosehaving ordinary skill in the art.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A superabsorbent polymer composition producedfrom an acrylic composition, wherein said acrylic composition comprisesan acrylic acid composition, wherein said acrylic acid compositionconsists of acrylic acid, acrylic acid derivatives, or mixtures thereof,wherein said acrylic acid composition comprises at least about 98 wt %acrylic acid, acrylic acid derivatives, or mixtures thereof, and whereina portion of the remaining impurities in said acrylic acid compositionis lactic acid, lactic acid derivatives, or mixtures thereof; andfurther, wherein said superabsorbent polymer is produced by the stepscomprising: a. Preparing a pre-polymerization solution comprisingglacial acrylic acid, methylene bis-acrylamide, and water; b. Mixingsodium hydroxide into said pre-polymerization solution to form apartially neutralized acrylic acid solution; c. Combining2,2′-azobis(2-methylpropionamidine)dihydrochloride with said partiallyneutralized acrylic acid solution to produce a polymerization mixture;d. Polymerizing said polymerization mixture using UV light to produce agel; and e. Drying said gel to produce the superabsorbent polymercomposition.
 2. The composition of claim 1, wherein the amount of saidacrylic acid composition in said pre-polymerization solution is fromabout 5 wt % to about 95 wt %.
 3. The superabsorbent polymer compositionof claim 1 having a bio-based content greater than about 3%.
 4. Thesuperabsorbent polymer composition of claim 1 having a bio-based contentgreater than about 30%.
 5. The superabsorbent polymer composition ofclaim 1 having a bio-based content greater than about 90%.
 6. Thesuperabsorbent polymer composition of claim 1, wherein said acrylic acidcomposition has a bio-based content greater than about 3%.
 7. Thesuperabsorbent polymer composition of claim 1, wherein said acrylic acidcomposition has a bio-based content greater than about 30%.
 8. Thesuperabsorbent polymer composition of claim 1, wherein said acrylic acidcomposition has a bio-based content greater than about 90%.
 9. Thesuperabsorbent polymer composition of claim 1, wherein said polymercomposition has a cylinder retention capacity (CRC) between about 20 g/gand about 45 g/g.
 10. The superabsorbent polymer composition of claim 1,wherein said polymer composition has a cylinder retention capacity (CRC)between about 25 g/g and about 40 g/g.
 11. The superabsorbent polymercomposition of claim 1, wherein said polymer composition has a cylinderretention capacity (CRC) between about 30 g/g and about 35 g/g.
 12. Thesuperabsorbent polymer composition of claim 1, wherein said polymercomposition has an extractables value from about 0 wt % to about 20 wt%.
 13. The superabsorbent polymer composition of claim 1, wherein saidpolymer composition has an extractables value from about 3 wt % to about15 wt %.
 14. The superabsorbent polymer composition of claim 1, whereinsaid polymer composition has an extractables value from about 5 wt % toabout 10 wt %.
 15. The superabsorbent polymer composition of claim 1,wherein said polymer composition has absorption against pressure (AAP)between about 15 g/g and about 40 g/g.
 16. The superabsorbent polymercomposition of claim 1, wherein said polymer composition has absorptionagainst pressure (AAP) between about 20 g/g and about 35 g/g.
 17. Thesuperabsorbent polymer composition of claim 1, wherein said polymercomposition has absorption against pressure (AAP) between about 25 g/gand about 30 g/g.
 18. The superabsorbent polymer composition of claim 1,wherein the amount of residual monomers in said polymer is about 500 ppmor less.
 19. An absorbent article selected from adult incontinencegarments, infant diapers, and feminine hygiene articles, comprising thesuperabsorbent polymer composition of claim
 1. 20. An absorbent articlehaving opposing longitudinal edges, the absorbent article comprising: a.a top sheet, b. a back sheet joined with the top sheet; and c. anabsorbent core disposed between the top sheet and the back sheet, andwherein, the absorbent core comprises a superabsorbent polymercomposition according to claim 1.